diff --git a/include/aws/lambda-runtime/runtime.h b/include/aws/lambda-runtime/runtime.h
index 46b8817..4d62789 100644
--- a/include/aws/lambda-runtime/runtime.h
+++ b/include/aws/lambda-runtime/runtime.h
@@ -85,6 +85,11 @@ class invocation_response {
      */
     bool m_success;
 
+    /**
+     * The serialized XRay response header.
+     */
+    std::string m_xray_response;
+
     /**
      * Instantiate an empty response. Used by the static functions 'success' and 'failure' to create a populated
      * invocation_response
@@ -102,6 +107,15 @@ class invocation_response {
     {
     }
 
+    invocation_response(
+        std::string const& payload,
+        std::string const& content_type,
+        bool success,
+        std::string const& xray_response)
+        : m_payload(payload), m_content_type(content_type), m_success(success), m_xray_response(xray_response)
+    {
+    }
+
     /**
      * Create a successful invocation response with the given payload and content-type.
      */
@@ -113,6 +127,11 @@ class invocation_response {
      */
     static invocation_response failure(std::string const& error_message, std::string const& error_type);
 
+    static invocation_response failure(
+        std::string const& error_message,
+        std::string const& error_type,
+        std::string const& xray_response);
+
     /**
      * Get the MIME type of the payload.
      */
@@ -127,6 +146,11 @@ class invocation_response {
      * Returns true if the payload and content-type are set. Returns false if the error message and error types are set.
      */
     bool is_success() const { return m_success; }
+
+    /**
+     * Get the XRay response string. The string isassumed to be UTF-8 encoded.
+     */
+    std::string const& get_xray_response() const { return m_xray_response; }
 };
 
 struct no_result {};
diff --git a/src/runtime.cpp b/src/runtime.cpp
index 1013a19..2a8825c 100644
--- a/src/runtime.cpp
+++ b/src/runtime.cpp
@@ -347,6 +347,10 @@ runtime::post_outcome runtime::do_post(
         headers = curl_slist_append(headers, ("content-type: " + handler_response.get_content_type()).c_str());
     }
 
+    if (!handler_response.get_xray_response().empty()) {
+        headers = curl_slist_append(
+            headers, ("lambda-runtime-function-xray-error-cause: " + handler_response.get_xray_response()).c_str());
+    }
     headers = curl_slist_append(headers, "Expect:");
     headers = curl_slist_append(headers, "transfer-encoding:");
     headers = curl_slist_append(headers, m_user_agent_header.c_str());
@@ -522,12 +526,22 @@ invocation_response invocation_response::success(std::string payload, std::strin
 
 AWS_LAMBDA_RUNTIME_API
 invocation_response invocation_response::failure(std::string const& error_message, std::string const& error_type)
+{
+    return failure(error_message, error_type, "");
+}
+
+AWS_LAMBDA_RUNTIME_API
+invocation_response invocation_response::failure(
+    std::string const& error_message,
+    std::string const& error_type,
+    std::string const& xray_response)
 {
     invocation_response r;
     r.m_success = false;
     r.m_content_type = "application/json";
     r.m_payload = R"({"errorMessage":")" + json_escape(error_message) + R"(","errorType":")" + json_escape(error_type) +
                   R"(","stackTrace":[]})";
+    r.m_xray_response = xray_response;
     return r;
 }