diff --git a/doc/releases/migration-guide-4.0.rst b/doc/releases/migration-guide-4.0.rst
index b68664387353991..5e45b2d2c302e01 100644
--- a/doc/releases/migration-guide-4.0.rst
+++ b/doc/releases/migration-guide-4.0.rst
@@ -404,6 +404,10 @@ Bluetooth Audio
 Bluetooth Host
 ==============
 
+* :c:func:`bt_gatt_subscribe` behavior has changed to if a different user/application has already
+  subscribed to the same handle, then the callback will contain the values aggregated of all the
+  users/applications.
+
 Automatic advertiser resumption is deprecated
 ---------------------------------------------
 
diff --git a/subsys/bluetooth/host/gatt.c b/subsys/bluetooth/host/gatt.c
index 5503bb6b8b99928..4b02bd0d1061a17 100644
--- a/subsys/bluetooth/host/gatt.c
+++ b/subsys/bluetooth/host/gatt.c
@@ -5429,7 +5429,7 @@ int bt_gatt_subscribe(struct bt_conn *conn,
 {
 	struct gatt_sub *sub;
 	struct bt_gatt_subscribe_params *tmp;
-	bool has_subscription = false;
+	int err;
 
 	__ASSERT(conn, "invalid parameters\n");
 	__ASSERT(params && params->notify,  "invalid parameters\n");
@@ -5446,6 +5446,11 @@ int bt_gatt_subscribe(struct bt_conn *conn,
 		return -ENOTCONN;
 	}
 
+	if (params->value < BT_GATT_CCC_NOTIFY
+		|| params->value > BT_GATT_CCC_INDICATE) {
+		return -EINVAL;
+	}
+
 	sub = gatt_sub_add(conn);
 	if (!sub) {
 		return -ENOMEM;
@@ -5467,26 +5472,20 @@ int bt_gatt_subscribe(struct bt_conn *conn,
 		}
 
 		/* Check if another subscription exists */
-		if (tmp->value_handle == params->value_handle &&
-		    tmp->value >= params->value) {
-			has_subscription = true;
+		if (tmp->value_handle == params->value_handle) {
+			params->value |= tmp->value;
 		}
 	}
 
-	/* Skip write if already subscribed */
-	if (!has_subscription) {
-		int err;
-
 #if defined(CONFIG_BT_GATT_AUTO_DISCOVER_CCC)
-		if (params->ccc_handle == BT_GATT_AUTO_DISCOVER_CCC_HANDLE) {
-			return gatt_ccc_discover(conn, params);
-		}
+	if (params->ccc_handle == BT_GATT_AUTO_DISCOVER_CCC_HANDLE) {
+		return gatt_ccc_discover(conn, params);
+	}
 #endif
-		err = gatt_write_ccc(conn, params, gatt_write_ccc_rsp);
-		if (err) {
-			gatt_sub_remove(conn, sub, NULL, NULL);
-			return err;
-		}
+	err = gatt_write_ccc(conn, params, gatt_write_ccc_rsp);
+	if (err) {
+		gatt_sub_remove(conn, sub, NULL, NULL);
+		return err;
 	}
 
 	/*