diff --git a/mail_notification_custom_subject/models/mail_message_custom_subject.py b/mail_notification_custom_subject/models/mail_message_custom_subject.py
index 0340b56305..53e169109d 100644
--- a/mail_notification_custom_subject/models/mail_message_custom_subject.py
+++ b/mail_notification_custom_subject/models/mail_message_custom_subject.py
@@ -21,6 +21,9 @@ class MailMessageCustomSubject(models.Model):
         string="Applied Subtypes",
         required=True,
     )
+    subject_to_replace = fields.Char(
+        help="Subject to replace (placeholders may be used here)"
+    )
     subject_template = fields.Char(
         required=True,
         translate=True,
@@ -31,8 +34,9 @@ class MailMessageCustomSubject(models.Model):
             ("append_before", "Append Before"),
             ("append_after", "Append After"),
             ("replace", "Replace"),
+            ("inside_replace", "Inside Replace"),
         ],
         default="replace",
-        help="Whether to replace, append at beggining or append at end to other"
-        " templates that apply to a given context",
+        help="Whether to replace, inside Replace, append at beggining or append at"
+        " end to other templates that apply to a given context",
     )
diff --git a/mail_notification_custom_subject/models/mail_thread.py b/mail_notification_custom_subject/models/mail_thread.py
index 08a26b32db..ddd6954f64 100644
--- a/mail_notification_custom_subject/models/mail_thread.py
+++ b/mail_notification_custom_subject/models/mail_thread.py
@@ -68,6 +68,23 @@ def message_post(
                         subject = rendered_subject_template + subject
                     elif template.position == "append_after":
                         subject += rendered_subject_template
+                    elif template.position == "inside_replace":
+                        try:
+                            rendered_subject_to_replace = self.env[
+                                "mail.template"
+                            ]._render_template(
+                                template_src=template.subject_to_replace,
+                                model=self._name,
+                                res_ids=[self.id],
+                            )[self.id]
+                            if rendered_subject_to_replace:
+                                # To avoid empty string replacements
+                                subject = subject.replace(
+                                    rendered_subject_to_replace,
+                                    rendered_subject_template,
+                                )
+                        except Exception:
+                            rendered_subject_to_replace = False
                 except Exception:
                     rendered_subject_template = False
         return super().message_post(
diff --git a/mail_notification_custom_subject/tests/test_mail_notification_custom_subject.py b/mail_notification_custom_subject/tests/test_mail_notification_custom_subject.py
index 08c37249af..a1e2bfe740 100644
--- a/mail_notification_custom_subject/tests/test_mail_notification_custom_subject.py
+++ b/mail_notification_custom_subject/tests/test_mail_notification_custom_subject.py
@@ -55,6 +55,27 @@ def test_email_subject_template_overrides(self):
         # Get message and check subject
         self.assertEqual(mail_message_3.subject, "Test")
 
+    def test_email_subject_template_inside_replace(self):
+        with self.with_user("boss"):
+            self.env["mail.message.custom.subject"].create(
+                {
+                    "name": "Test template",
+                    "model_id": self.env.ref("base.model_res_partner").id,
+                    "subtype_ids": [(6, 0, [self.env.ref("mail.mt_comment").id])],
+                    "subject_to_replace": "{{object.company_id.name}}",
+                    "subject_template": "CLN",
+                    "position": "inside_replace",
+                }
+            )
+        self.partner_1.company_id = self.env.company
+        self.partner_1.company_id.name = "COMPANY_LONG_NAME"
+        mail_message_1 = self.partner_1.message_post(
+            subject="COMPANY_LONG_NAME: Custom",
+            body="Test",
+            subtype_xmlid="mail.mt_comment",
+        )
+        self.assertEqual(mail_message_1.subject, "CLN: Custom")
+
     def test_email_subject_template_normal(self):
         with self.with_user("boss"):
             self.env["mail.message.custom.subject"].create(
diff --git a/mail_notification_custom_subject/views/mail_notification_custom_subject_views.xml b/mail_notification_custom_subject/views/mail_notification_custom_subject_views.xml
index 3267af9fbb..ee91309f49 100644
--- a/mail_notification_custom_subject/views/mail_notification_custom_subject_views.xml
+++ b/mail_notification_custom_subject/views/mail_notification_custom_subject_views.xml
@@ -11,6 +11,11 @@
                         <h1 name="name"><field name="name" /></h1>
                     </div>
                     <group>
+                        <field
+                            name="subject_to_replace"
+                            invisible="position!='inside_replace'"
+                            required="position=='inside_replace'"
+                        />
                         <field
                             name="subject_template"
                             placeholder="Subject (placeholders may be used here)"