diff --git a/specification/datafactory/resource-manager/Microsoft.DataFactory/preview/2017-09-01-preview/entityTypes/Pipeline.json b/specification/datafactory/resource-manager/Microsoft.DataFactory/preview/2017-09-01-preview/entityTypes/Pipeline.json
index 856bfc7a6ce7..24c5ecaea9e7 100644
--- a/specification/datafactory/resource-manager/Microsoft.DataFactory/preview/2017-09-01-preview/entityTypes/Pipeline.json
+++ b/specification/datafactory/resource-manager/Microsoft.DataFactory/preview/2017-09-01-preview/entityTypes/Pipeline.json
@@ -2799,6 +2799,49 @@
         "activities"
       ]
     },
+    "ValidationActivity": {
+      "x-ms-discriminator-value": "Validation",
+      "description": "This activity blocks execution until a file has been validated to exist with an optional minimum size or timeout is reached, whichever is earlier.",
+      "allOf": [
+        {
+          "$ref": "#/definitions/ControlActivity"
+        }
+      ],
+      "properties": {
+        "typeProperties": {
+          "description": "Validation activity properties.",
+          "x-ms-client-flatten": true,
+          "$ref": "#/definitions/ValidationActivityTypeProperties"
+        }
+      },
+      "required": [
+        "typeProperties"
+      ]
+    },
+    "ValidationActivityTypeProperties": {
+      "description": "Validation activity properties.",
+      "properties": {
+        "timeout": {
+          "type": "object",
+          "description": "Specifies the timeout for the activity to run. If there is no value specified, it takes the value of TimeSpan.FromDays(7) which is 1 week as default. Type: string (or Expression with resultType string), pattern: ((\\d+)\\.)?(\\d\\d):(60|([0-5][0-9])):(60|([0-5][0-9])). Type: string (or Expression with resultType string), pattern: ((\\d+)\\.)?(\\d\\d):(60|([0-5][0-9])):(60|([0-5][0-9]))."
+        },
+        "sleep": {
+          "description": "A delay in seconds between validation attempts. If no value is specified, 10 seconds will be used as the default.",
+          "type": "integer"
+        },
+        "minimumSize": {
+          "description": "Minimum size of a file in byte. If no value is specified, 0 byte will be used as the default.",
+          "type": "integer"
+        },
+        "dataset": {
+          "description": "Validation activity dataset reference.",
+          "$ref": "../datafactory.json#/definitions/DatasetReference"
+        }
+      },
+      "required": [
+        "dataset"
+      ]
+    },
     "FilterActivity": {
       "x-ms-discriminator-value": "Filter",
       "description": "Filter and return results from input array based on the conditions.",