diff --git a/MockerTests/MockerTests.swift b/MockerTests/MockerTests.swift
index 819682f..0ce11ed 100644
--- a/MockerTests/MockerTests.swift
+++ b/MockerTests/MockerTests.swift
@@ -268,7 +268,7 @@ final class MockerTests: XCTestCase {
         let onRequestExpectation = expectation(description: "Data request should start")
         let completionExpectation = expectation(description: "Data request should succeed")
         var mock = Mock(dataType: .json, statusCode: 200, data: [.get: Data()])
-        mock.onRequest = {
+        mock.onRequest = { _, _ in
             onRequestExpectation.fulfill()
         }
         mock.completion = {
@@ -281,6 +281,28 @@ final class MockerTests: XCTestCase {
         wait(for: [onRequestExpectation, completionExpectation], timeout: 2.0, enforceOrder: true)
     }
 
+    /// It should report post body arguments if they exist.
+    func testOnRequestPostBodyParameters() throws {
+        let onRequestExpectation = expectation(description: "Data request should start")
+
+        let expectedParameters = ["test": "value"]
+        var request = URLRequest(url: URL(string: "https://www.fakeurl.com")!)
+        request.httpMethod = Mock.HTTPMethod.post.rawValue
+        request.httpBody = try JSONSerialization.data(withJSONObject: expectedParameters, options: .prettyPrinted)
+
+        var mock = Mock(url: request.url!, dataType: .json, statusCode: 200, data: [.post: Data()])
+        mock.onRequest = { request, postBodyArguments in
+            XCTAssertEqual(request.url, mock.request.url)
+            XCTAssertEqual(expectedParameters, postBodyArguments as? [String: String])
+            onRequestExpectation.fulfill()
+        }
+        mock.register()
+
+        URLSession.shared.dataTask(with: request).resume()
+
+        wait(for: [onRequestExpectation], timeout: 2.0)
+    }
+
     /// It should call the mock after a delay.
     func testDelayedMock() {
         let nonDelayExpectation = expectation(description: "Data request should succeed")
diff --git a/README.md b/README.md
index 8d447d7..02feb7d 100644
--- a/README.md
+++ b/README.md
@@ -28,6 +28,7 @@ Mocker is a library written in Swift which makes it possible to mock data reques
 	    - [Delayed responses](#delayed-responses)
 	    - [Redirect responses](#redirect-responses)
 	    - [Ignoring URLs](#ignoring-urls)
+	    - [Mock callbacks](#mock-callbacks)
 - [Communication](#communication)
 - [Installation](#installation)
 - [Release Notes](#release-notes)
@@ -186,6 +187,23 @@ let ignoredURL = URL(string: "www.wetransfer.com")!
 Mocker.ignore(ignoredURL)
 ```
 
+##### Mock callbacks
+You can register on `Mock` callbacks to make testing easier.
+
+```swift
+var mock = Mock(url: request.url!, dataType: .json, statusCode: 200, data: [.post: Data()])
+mock.onRequest = { request, postBodyArguments in
+    XCTAssertEqual(request.url, mock.request.url)
+    XCTAssertEqual(expectedParameters, postBodyArguments as? [String: String])
+    onRequestExpectation.fulfill()
+}
+mock.completion = {
+    endpointIsCalledExpectation.fulfill()
+}
+mock.register()
+```
+
+
 ## Communication
 
 - If you **found a bug**, open an issue.
diff --git a/Sources/Mock.swift b/Sources/Mock.swift
index 023330b..8b0be4b 100644
--- a/Sources/Mock.swift
+++ b/Sources/Mock.swift
@@ -12,7 +12,7 @@ import Foundation
 
 /// A Mock which can be used for mocking data requests with the `Mocker` by calling `Mocker.register(...)`.
 public struct Mock: Equatable {
-    
+
     /// HTTP method definitions.
     ///
     /// See https://tools.ietf.org/html/rfc7231#section-4.3
@@ -54,6 +54,8 @@ public struct Mock: Equatable {
             }
         }
     }
+
+    public typealias OnRequest = (_ request: URLRequest, _ httpBodyArguments: [String: Any]?) -> Void
     
     /// The type of the data which is returned.
     public let dataType: DataType
@@ -97,7 +99,7 @@ public struct Mock: Equatable {
     public var completion: (() -> Void)?
 
     /// The callback which will be executed everytime this `Mock` was started. Can be used within unit tests for validating that a request has been started.
-    public var onRequest: (() -> Void)?
+    public var onRequest: OnRequest?
     
     private init(url: URL? = nil, ignoreQuery: Bool = false, dataType: DataType, statusCode: Int, data: [HTTPMethod: Data], additionalHeaders: [String: String] = [:], fileExtensions: [String]? = nil) {
         self.urlToMock = url
diff --git a/Sources/MockingURLProtocol.swift b/Sources/MockingURLProtocol.swift
index 21d29a5..51997ba 100644
--- a/Sources/MockingURLProtocol.swift
+++ b/Sources/MockingURLProtocol.swift
@@ -40,7 +40,9 @@ public final class MockingURLProtocol: URLProtocol {
             return
         }
 
-        mock.onRequest?()
+        if let onRequest = mock.onRequest {
+            onRequest(request, request.postBodyArguments)
+        }
 
         guard let delay = mock.delay else {
             finishRequest(for: mock, data: data, response: response)
@@ -97,3 +99,32 @@ private extension Data {
         return redirectLocation
     }
 }
+
+private extension URLRequest {
+    var postBodyArguments: [String: Any]? {
+        guard let httpBody = httpBodyStreamData() else { return nil }
+        return try? JSONSerialization.jsonObject(with: httpBody, options: .fragmentsAllowed) as? [String: Any]
+    }
+
+    /// We need to use the http body stream data as the URLRequest once launched converts the `httpBody` to this stream of data.
+    private func httpBodyStreamData() -> Data? {
+        guard let bodyStream = self.httpBodyStream else { return nil }
+
+        bodyStream.open()
+
+        // Will read 16 chars per iteration. Can use bigger buffer if needed
+        let bufferSize: Int = 16
+        let buffer = UnsafeMutablePointer<UInt8>.allocate(capacity: bufferSize)
+        var data = Data()
+
+        while bodyStream.hasBytesAvailable {
+            let readData = bodyStream.read(buffer, maxLength: bufferSize)
+            data.append(buffer, count: readData)
+        }
+
+        buffer.deallocate()
+        bodyStream.close()
+
+        return data
+    }
+}