diff --git a/src/common/config/classes.ts b/src/common/config/classes.ts
index e12a4c66..a605d172 100644
--- a/src/common/config/classes.ts
+++ b/src/common/config/classes.ts
@@ -433,6 +433,15 @@ export class HomeassistantConfig extends NotifierConfig {
   @IsString()
   notifyservice: string;
 
+  /**
+   * A key-value pair object to additionally pass into the service's `data` object
+   * @example { "parse_mode": "html" }
+   * @env HOMEASSISTANT_CUSTOM_DATA (stringified JSON)
+   */
+  @IsObject()
+  @IsOptional()
+  customData: Record<string, boolean | number | string> | undefined;
+
   /**
    * @ignore
    */
@@ -1088,6 +1097,7 @@ export class AppConfig {
       HOMEASSISTANT_INSTANCE,
       HOMEASSISTANT_LONG_LIVED_ACCESS_TOKEN,
       HOMEASSISTANT_NOTIFYSERVICE,
+      HOMEASSISTANT_CUSTOM_DATA,
     } = process.env;
     if (
       HOMEASSISTANT_INSTANCE &&
@@ -1098,6 +1108,9 @@ export class AppConfig {
       homeassistant.instance = HOMEASSISTANT_INSTANCE;
       homeassistant.token = HOMEASSISTANT_LONG_LIVED_ACCESS_TOKEN;
       homeassistant.notifyservice = HOMEASSISTANT_NOTIFYSERVICE;
+      homeassistant.customData = HOMEASSISTANT_CUSTOM_DATA
+        ? JSON.parse(HOMEASSISTANT_CUSTOM_DATA)
+        : undefined;
       if (!this.notifiers) {
         this.notifiers = [];
       }
diff --git a/src/notifiers/homeassistant.ts b/src/notifiers/homeassistant.ts
index 42bbee7c..034c2a33 100644
--- a/src/notifiers/homeassistant.ts
+++ b/src/notifiers/homeassistant.ts
@@ -25,6 +25,7 @@ export class HomeassistantNotifier extends NotifierService {
           data: {
             url,
             clickAction: url,
+            ...(this.config.customData ?? {}),
           },
         },
         {