diff --git a/Gemfile b/Gemfile
index b5eb2a20..44464793 100644
--- a/Gemfile
+++ b/Gemfile
@@ -24,7 +24,7 @@ gem 'strong_parameters'
 gem 'swfobject-rails'
 gem 'tddium'
 gem 'thin'
-gem 'yam', '0.0.6'
+gem 'yam', '~> 2.0.0'
 gem 'zclip-rails'
 
 # Gems used only for assets, not required in production environments by default.
diff --git a/Gemfile.lock b/Gemfile.lock
index 410c1c16..eefd14e3 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -28,7 +28,7 @@ GEM
     activesupport (3.2.16)
       i18n (~> 0.6, >= 0.6.4)
       multi_json (~> 1.0)
-    addressable (2.3.3)
+    addressable (2.3.5)
     airbrake (3.1.8)
       activesupport
       builder
@@ -96,11 +96,9 @@ GEM
     factory_girl_rails (4.2.1)
       factory_girl (~> 4.2.0)
       railties (>= 3.0.0)
-    faraday (0.8.5)
-      multipart-post (~> 1.1)
-    faraday_middleware (0.9.0)
-      faraday (>= 0.7.4, < 0.9)
-    ffi (1.9.3)
+    faraday (0.8.8)
+      multipart-post (~> 1.2.0)
+    ffi (1.4.0)
     flutie (1.3.3)
     foreman (0.61.0)
       thor (>= 0.13.6)
@@ -144,9 +142,9 @@ GEM
     jquery-rails (2.2.1)
       railties (>= 3.0, < 5.0)
       thor (>= 0.14, < 2.0)
-    json (1.7.7)
-    jwt (0.1.5)
-      multi_json (>= 1.0)
+    json (1.8.1)
+    jwt (0.1.8)
+      multi_json (>= 1.5)
     launchy (2.2.0)
       addressable (~> 2.3)
     listen (0.7.3)
@@ -160,15 +158,16 @@ GEM
     mime-types (1.25.1)
     multi_json (1.8.2)
     multi_xml (0.5.3)
-    multipart-post (1.1.5)
+    multipart-post (1.2.0)
     newrelic_rpm (3.5.6.55)
     nokogiri (1.5.6)
-    oauth2 (0.8.0)
+    oauth2 (0.8.1)
       faraday (~> 0.8)
       httpauth (~> 0.1)
       jwt (~> 0.1.4)
       multi_json (~> 1.0)
       rack (~> 1.2)
+    oj (2.0.14)
     omniauth (1.1.3)
       hashie (~> 1.2)
       rack
@@ -221,6 +220,8 @@ GEM
     rake (10.1.0)
     rdoc (3.12.2)
       json (~> 1.4)
+    rest-client (1.6.7)
+      mime-types (>= 1.16)
     rspec (2.14.1)
       rspec-core (~> 2.14.0)
       rspec-expectations (~> 2.14.0)
@@ -305,13 +306,11 @@ GEM
     websocket (1.0.7)
     xpath (1.0.0)
       nokogiri (~> 1.3)
-    yam (0.0.6)
-      faraday (~> 0.8.1)
-      faraday_middleware (~> 0.9.0)
-      hashie (~> 1.2.0)
-      json (~> 1.7.6)
+    yam (2.0.0)
+      addressable (~> 2.3.3)
       multi_json (~> 1.3)
-      oauth2 (~> 0.8.0)
+      oj (~> 2.0.10)
+      rest-client (~> 1.6.7)
     zclip-rails (0.0.1)
       jquery-rails (>= 1.0.17)
       railties (~> 3.1)
@@ -370,5 +369,5 @@ DEPENDENCIES
   timecop
   turnip (= 1.0)
   uglifier (>= 1.0)
-  yam (= 0.0.6)
+  yam (~> 2.0.0)
   zclip-rails
diff --git a/app/controllers/sessions_controller.rb b/app/controllers/sessions_controller.rb
index c4a5cea9..3d4cd07f 100644
--- a/app/controllers/sessions_controller.rb
+++ b/app/controllers/sessions_controller.rb
@@ -49,7 +49,7 @@ def find_or_instantiate_user
   end
 
   def refresh_user_data_from_yammer(user)
-    yammer_user_data = user.yammer_client.get("/users/#{omniauth[:uid]}")
+    yammer_user_data = user.yammer_client.get_user(omniauth[:uid]).body
     YammerUserResponseTranslator.
       new(yammer_user_data, user).
       translate.
diff --git a/app/controllers/yammer_user_invitations_controller.rb b/app/controllers/yammer_user_invitations_controller.rb
index 6bde7a60..46876838 100644
--- a/app/controllers/yammer_user_invitations_controller.rb
+++ b/app/controllers/yammer_user_invitations_controller.rb
@@ -23,7 +23,7 @@ def args
   end
 
   def create_user_from(invitee_id)
-    invitee_data = owner_yammer_client.get("/users/#{invitee_id}")
+    invitee_data = owner_yammer_client.get_user(invitee_id).body
     User.new.tap do |user|
       YammerUserResponseTranslator.
         new(invitee_data, user).
diff --git a/app/jobs/activity_creator_job.rb b/app/jobs/activity_creator_job.rb
index e0f5a6d2..55512a38 100644
--- a/app/jobs/activity_creator_job.rb
+++ b/app/jobs/activity_creator_job.rb
@@ -19,7 +19,7 @@ def user
   end
 
   def post_yammer_activity
-    user.yammer_client.post('/activity', json_payload)
+    user.yammer_client.create_activity(json_payload)
   end
 
   def json_payload
diff --git a/app/models/invitee_builder.rb b/app/models/invitee_builder.rb
index b0786b04..a273988d 100644
--- a/app/models/invitee_builder.rb
+++ b/app/models/invitee_builder.rb
@@ -31,10 +31,7 @@ def get_user_from_yammer
   end
 
   def get_yammer_user_by_email
-    @event.owner.
-      yammer_client.
-      get('/users/by_email', email: @email).
-      try(:first)
+    @event.owner.yammer_client.get_user_by_email(@email).try(:body).try(:first)
   end
 
   def create_guest
diff --git a/app/models/user.rb b/app/models/user.rb
index fbf195b3..3bdc71a3 100644
--- a/app/models/user.rb
+++ b/app/models/user.rb
@@ -1,3 +1,5 @@
+require 'yammer'
+
 class User < ActiveRecord::Base
   attr_encrypted :access_token, key: ENV['ACCESS_TOKEN_ENCRYPTION_KEY']
 
@@ -90,7 +92,7 @@ def yammer_client
       raise 'Yammer client requires an access_token!'
     end
 
-    @yam ||= Yam.new(access_token, yammer_endpoint)
+    @yam ||= Yammer::Client.new(access_token: access_token)
   end
 
   private
@@ -107,18 +109,6 @@ def messenger(sender)
     end
   end
 
-  def yammer_endpoint
-    "#{yammer_host}/api/v1/"
-  end
-
-  def yammer_host
-    if yammer_staging
-      Rails.configuration.yammer_staging_host
-    else
-      Rails.configuration.yammer_host
-    end
-  end
-
   def strip_email_whitespace
     self.email = email.try(:strip)
   end
diff --git a/app/models/yammer_messenger.rb b/app/models/yammer_messenger.rb
index 9b267bae..fff8d882 100644
--- a/app/models/yammer_messenger.rb
+++ b/app/models/yammer_messenger.rb
@@ -35,7 +35,7 @@ def notify(event, message)
   private
 
   def deliver
-    @sender.yammer_client.post('/messages', request_params)
+    @sender.yammer_client.create_message(message_body, request_params)
   end
 
   def request_params
diff --git a/app/models/yammer_user_response_translator.rb b/app/models/yammer_user_response_translator.rb
index 67e8f220..1ea26c2e 100644
--- a/app/models/yammer_user_response_translator.rb
+++ b/app/models/yammer_user_response_translator.rb
@@ -19,11 +19,34 @@ def translate
 
   private
 
+  # def parse_email_from_response
+  #   if @response && @response[:contact] && @response[:contact][:email_addresses]
+  #     primary_email = @response[:contact][:email_addresses].
+  #       detect{ |address| address[:type] == 'primary' }
+  #     primary_email && primary_email[:address]
+  #   end
+  # end
+
+
   def parse_email_from_response
-    if @response && @response['contact'] && @response['contact']['email_addresses']
-      primary_email = @response['contact']['email_addresses'].
-        detect{ |address| address['type'] == 'primary' }
-      primary_email && primary_email['address']
+    if valid_response?
+      primary_email && primary_email_address
     end
   end
+
+  def valid_response?
+    @response && @response[:contact] && @response[:contact][:email_addresses]
+  end
+
+  def primary_email
+    all_email_addresses.detect{ |address| address[:type] == 'primary' }
+  end
+
+  def all_email_addresses
+    @response[:contact][:email_addresses]
+  end
+
+  def primary_email_address
+    primary_email[:address]
+  end
 end
diff --git a/spec/acceptance/owner_can_invite_users_using_the_viral_invite.feature b/spec/acceptance/owner_can_invite_users_using_the_viral_invite.feature
index f978af04..ef188a70 100644
--- a/spec/acceptance/owner_can_invite_users_using_the_viral_invite.feature
+++ b/spec/acceptance/owner_can_invite_users_using_the_viral_invite.feature
@@ -63,7 +63,7 @@ Feature: Multiple invitations
     And I invite the Yammer user "Joe Smith" to "Clown party" from the multiple invite page
     And I remove "Joe Smith" from the list of invited users
     When I press the "Invite" button for the "Clown party" event
-    Then "Joe Smith" should receive 0 private message
+    Then "Joe Smith" should receive 0 private messages
     And I should not see "Joe Smith" in the list of invitees
 
   @javascript
diff --git a/spec/acceptance/step_definitions/invitation_steps.rb b/spec/acceptance/step_definitions/invitation_steps.rb
index 12a4ecc3..f6c057fb 100644
--- a/spec/acceptance/step_definitions/invitation_steps.rb
+++ b/spec/acceptance/step_definitions/invitation_steps.rb
@@ -56,14 +56,14 @@
 
 step 'someone invites :email to :event_name' do |email, event_name|
   event = Event.find_by_name!(event_name)
-  invitation = Invitation.new(event: event)
-  InviteeBuilder.new.find_user_by_email_or_create_guest(email, event).save
+  user = InviteeBuilder.new(email, event).find_user_by_email_or_create_guest
+  create(:invitation, event: event, invitee: user)
 end
 
 step ':guest_email was invited to the event :event_name' do |guest_email, event_name|
   event = Event.find_by_name!(event_name)
-  invitation = Invitation.new(event: event)
-  InviteeBuilder.new(guest_email, event).find_user_by_email_or_create_guest.save
+  user = InviteeBuilder.new(guest_email, event).find_user_by_email_or_create_guest
+  create(:invitation, event: event, invitee: user)
 end
 
 # Multi-invite page
@@ -114,7 +114,7 @@
 end
 
 step ':first_item should appear before :second_item' do |first_item, second_item|
-  expect(page.body).to match /#{first_item}.*#{second_item}/m
+  expect(page.body).to match(/#{first_item}.*#{second_item}/m)
 end
 
 step ':name should receive a private message' do |name|
diff --git a/spec/acceptance/step_definitions/yammer_user_steps.rb b/spec/acceptance/step_definitions/yammer_user_steps.rb
index 11eed1b0..f58b7238 100644
--- a/spec/acceptance/step_definitions/yammer_user_steps.rb
+++ b/spec/acceptance/step_definitions/yammer_user_steps.rb
@@ -3,25 +3,25 @@
 end
 
 step 'a Yammer user exists named :name with email :email' do |name, email|
-  yammer = Yam.new('123', 'https://www.yammer.com/api/v1')
+  yammer = Yammer::Client.new(access_token: '123')
   FakeYammer.yammer_user_name = name
   FakeYammer.yammer_email = email
-  users = yammer.get('/users/by_email', email: email)
-  expect(users[0]['id']).to be_present
+  users = yammer.get_user_by_email(email).body
+  expect(users[0][:id]).to be_present
 end
 
 step 'no Yammer user exists with email :email' do |email|
-  yammer = Yam.new('123', 'https://www.yammer.com/api/v1')
+  yammer = Yammer::Client.new(access_token: '123')
   FakeYammer.yammer_user_name = 'Wrong Name'
   FakeYammer.yammer_email = email + '.fake'
-  users = yammer.get('/users/by_email', email: email)
-  expect(users.first).to_not be_present
+  users = yammer.get_user_by_email(email).body
+  expect(users).to_not be_present
 end
 
 step ':email signs up for Yammer as :name' do |email, name|
-  yammer = Yam.new('123', 'https://www.yammer.com/api/v1')
+  yammer = Yammer::Client.new(access_token: '123')
   FakeYammer.yammer_user_name = name
   FakeYammer.yammer_email = email
-  users = yammer.get('/users/by_email', email: email)
-  expect(users[0]['id']).to be_present
+  users = yammer.get_user_by_email(email).body
+  expect(users[0][:id]).to be_present
 end
diff --git a/spec/controllers/invitations_controller_spec.rb b/spec/controllers/invitations_controller_spec.rb
index d22a0c62..09c35a14 100644
--- a/spec/controllers/invitations_controller_spec.rb
+++ b/spec/controllers/invitations_controller_spec.rb
@@ -80,7 +80,7 @@
     it 'creates multiple invitations for the correct users' do
       event_creator = create_user_and_sign_in
       event = create(:event, owner: event_creator)
-      invitation = double(invite: nil, valid?: true)
+      invitation = double(invite: nil, invite: nil, valid?: true)
       emails = 'guest1@example.com, guest2@example.com'
       Invitation.stub(new: invitation)
       invitee = double
diff --git a/spec/jobs/activity_creator_job_spec.rb b/spec/jobs/activity_creator_job_spec.rb
index ae526922..f8f59c85 100644
--- a/spec/jobs/activity_creator_job_spec.rb
+++ b/spec/jobs/activity_creator_job_spec.rb
@@ -23,13 +23,13 @@
     event = build_stubbed(:event)
     User.stub(find: user)
     Event.stub(find: event)
-    yam_session_stub = double(post: nil)
-    Yam.stub(new: yam_session_stub)
+    yam_session = double(create_activity: nil)
+    Yammer::Client.stub(new: yam_session)
 
     ActivityCreatorJob.new(user, action, event).perform
 
-    expect(yam_session_stub).to have_received(:post).
-      with('/activity', expected_json(event))
+    expect(yam_session).to have_received(:create_activity).
+      with(expected_json(event))
   end
 
   private
diff --git a/spec/jobs/vote_created_job_spec.rb b/spec/jobs/vote_created_job_spec.rb
index 60ecfe96..0769c6fb 100644
--- a/spec/jobs/vote_created_job_spec.rb
+++ b/spec/jobs/vote_created_job_spec.rb
@@ -70,7 +70,7 @@
 
       VoteCreatedJob.new.perform
 
-      expect(voter.yammer_client.oauth_token).to eq voter.access_token
+      expect(voter.yammer_client.access_token).to eq voter.access_token
     end
   end
 
diff --git a/spec/models/invitee_builder_spec.rb b/spec/models/invitee_builder_spec.rb
index e296d85d..9068181d 100644
--- a/spec/models/invitee_builder_spec.rb
+++ b/spec/models/invitee_builder_spec.rb
@@ -27,13 +27,13 @@
     it 'searches for existing Yammer users' do
       invitation = create(:invitation)
       invitee_email = 'ralph@example.com'
-      yam_client = double(get: nil)
-      Yam.stub(new: yam_client)
+      yam_client = double(get_user_by_email: nil)
+      Yammer::Client.stub(new: yam_client)
 
       InviteeBuilder.new(invitee_email, invitation.event).
         find_user_by_email_or_create_guest
 
-      expect(yam_client).to have_received(:get)
+      expect(yam_client).to have_received(:get_user_by_email)
     end
 
     it 'creates a User if it finds an existing Yammer user' do
diff --git a/spec/models/yammer_user_response_translator_spec.rb b/spec/models/yammer_user_response_translator_spec.rb
index 2e762b21..b82db488 100644
--- a/spec/models/yammer_user_response_translator_spec.rb
+++ b/spec/models/yammer_user_response_translator_spec.rb
@@ -10,11 +10,13 @@
         web_url: 'http://web_url',
         network_id: 2,
         network_name: 'network',
-        'contact' => {
-          'email_addresses' => [{
-            'type' => 'primary',
-            'address' => 'a@b.com'
-          }]
+        contact: {
+          email_addresses: [
+            {
+              type: 'primary',
+              address: 'a@b.com'
+            }
+          ]
         }
       }
       user = User.new
diff --git a/spec/support/fake_yammer.rb b/spec/support/fake_yammer.rb
index 51b133f2..fdf325a0 100644
--- a/spec/support/fake_yammer.rb
+++ b/spec/support/fake_yammer.rb
@@ -25,7 +25,7 @@ def self.reset
   end
 
   post '/api/v1/messages' do
-    self.access_token = params[:access_token]
+    self.access_token = self.request.env["HTTP_AUTHORIZATION"].split.last
     self.group_id = params[:group_id]
     self.message = params[:body]
     self.messages_endpoint_hits += 1
@@ -37,8 +37,6 @@ def self.reset
 
     if params[:email] == self.yammer_email
       json_for_user_email_search
-    else
-      "[ ]"
     end
   end