diff --git a/src/Stratis.Bitcoin.Features.Api/NodeController.cs b/src/Stratis.Bitcoin.Features.Api/NodeController.cs
index 596d11db50..17019e21c6 100644
--- a/src/Stratis.Bitcoin.Features.Api/NodeController.cs
+++ b/src/Stratis.Bitcoin.Features.Api/NodeController.cs
@@ -220,33 +220,34 @@ public IActionResult Status([FromQuery] bool publish)
         /// <param name="hash">The hash of the block to retrieve.</param>
         /// <param name="isJsonFormat">A flag that specifies whether to return the block header in the JSON format. Defaults to true. A value of false is currently not supported.</param>
         /// <returns>Json formatted <see cref="BlockHeaderModel"/>. <c>null</c> if block not found. Returns <see cref="Microsoft.AspNetCore.Mvc.IActionResult"/> formatted error if fails.</returns>
-        /// <exception cref="NotImplementedException">Thrown if isJsonFormat = false</exception>"
-        /// <exception cref="ArgumentException">Thrown if hash is empty.</exception>
-        /// <exception cref="ArgumentNullException">Thrown if logger is not provided.</exception>
+        /// <response code="200">Returns the blockheader if found.</response>
+        /// <response code="400">Null hash provided, BlockHeader does not exist or if isJsonFormat = false>/response>
         /// <remarks>Binary serialization is not supported with this method.</remarks>
         [Route("getblockheader")]
         [HttpGet]
+        [ProducesResponseType((int)HttpStatusCode.OK)]
+        [ProducesResponseType((int)HttpStatusCode.BadRequest)]
+        [ProducesResponseType((int)HttpStatusCode.NotFound)]
         public IActionResult GetBlockHeader([FromQuery] string hash, bool isJsonFormat = true)
         {
             try
             {
-                Guard.NotEmpty(hash, nameof(hash));
+                if (string.IsNullOrEmpty(hash))
+                    return ErrorHelpers.BuildErrorResponse(HttpStatusCode.BadRequest, "Error", "Null hash provided.");
 
                 this.logger.LogDebug("GetBlockHeader {0}", hash);
+
                 if (!isJsonFormat)
                 {
                     this.logger.LogError("Binary serialization is not supported.");
-                    throw new NotImplementedException();
+                    return ErrorHelpers.BuildErrorResponse(HttpStatusCode.BadRequest, "Error", "Binary serialization is not supported.");
                 }
 
-                BlockHeaderModel model = null;
                 BlockHeader blockHeader = this.chainIndexer?.GetHeader(uint256.Parse(hash))?.Header;
-                if (blockHeader != null)
-                {
-                    model = new BlockHeaderModel(blockHeader);
-                }
+                if (blockHeader == null)
+                    return this.NotFound($"Block header for '{hash}' not found");
 
-                return this.Json(model);
+                return this.Json(new BlockHeaderModel(blockHeader));
             }
             catch (Exception e)
             {
diff --git a/src/Stratis.Bitcoin.Features.BlockStore.Tests/BlockStoreControllerTests.cs b/src/Stratis.Bitcoin.Features.BlockStore.Tests/BlockStoreControllerTests.cs
index 612f5cd55a..55730a8d4b 100644
--- a/src/Stratis.Bitcoin.Features.BlockStore.Tests/BlockStoreControllerTests.cs
+++ b/src/Stratis.Bitcoin.Features.BlockStore.Tests/BlockStoreControllerTests.cs
@@ -68,9 +68,9 @@ public void Get_Block_When_Hash_Is_Not_Found_Should_Return_OkResult_WithMessage(
 
             IActionResult response = controller.GetBlock(new SearchByHashRequest() { Hash = new uint256(1).ToString(), OutputJson = true });
 
-            response.Should().BeOfType<OkObjectResult>();
-            var result = (OkObjectResult)response;
-            result.StatusCode.Should().Be((int)HttpStatusCode.OK);
+            response.Should().BeOfType<NotFoundObjectResult>();
+            var result = (NotFoundObjectResult)response;
+            result.StatusCode.Should().Be((int)HttpStatusCode.NotFound);
             result.Value.Should().Be("Block not found");
         }
 
diff --git a/src/Stratis.Bitcoin.Features.BlockStore/Controllers/BlockStoreController.cs b/src/Stratis.Bitcoin.Features.BlockStore/Controllers/BlockStoreController.cs
index d7c5500ef9..a413d28f13 100644
--- a/src/Stratis.Bitcoin.Features.BlockStore/Controllers/BlockStoreController.cs
+++ b/src/Stratis.Bitcoin.Features.BlockStore/Controllers/BlockStoreController.cs
@@ -122,6 +122,7 @@ public IActionResult GetAddressIndexerTip()
         [HttpGet]
         [ProducesResponseType((int)HttpStatusCode.OK)]
         [ProducesResponseType((int)HttpStatusCode.BadRequest)]
+        [ProducesResponseType((int)HttpStatusCode.NotFound)]
         public IActionResult GetBlock([FromQuery] SearchByHashRequest query)
         {
             if (!this.ModelState.IsValid)
@@ -134,14 +135,14 @@ public IActionResult GetBlock([FromQuery] SearchByHashRequest query)
                 ChainedHeader chainedHeader = this.chainIndexer.GetHeader(blockId);
 
                 if (chainedHeader == null)
-                    return this.Ok("Block not found");
+                    return this.NotFound("Block not found");
 
                 Block block = chainedHeader.Block ?? this.blockStore.GetBlock(blockId);
 
                 // In rare occasions a block that is found in the
                 // indexer may not have been pushed to the store yet. 
                 if (block == null)
-                    return this.Ok("Block not found");
+                    return this.NotFound("Block not found");
 
                 if (!query.OutputJson)
                 {
diff --git a/src/Stratis.Bitcoin.Tests/Controllers/NodeControllerTest.cs b/src/Stratis.Bitcoin.Tests/Controllers/NodeControllerTest.cs
index df7a3dba37..8b6c538072 100644
--- a/src/Stratis.Bitcoin.Tests/Controllers/NodeControllerTest.cs
+++ b/src/Stratis.Bitcoin.Tests/Controllers/NodeControllerTest.cs
@@ -526,7 +526,7 @@ public void GetBlockHeader_NotUsingJsonFormat_ThrowsNotImplementedException()
             Assert.Single(errorResponse.Errors);
             ErrorModel error = errorResponse.Errors[0];
             Assert.Equal(400, error.Status);
-            Assert.StartsWith("System.NotImplementedException", error.Description);
+            Assert.StartsWith("Binary serialization is not", error.Description);
         }
 
         [Fact]
@@ -555,10 +555,7 @@ public void GetBlockHeader_BlockHeaderNotFound_ReturnsNull()
             string hash = new uint256(2562).ToString();
             bool isJsonFormat = true;
 
-            var json = (JsonResult)this.controller.GetBlockHeader(hash, isJsonFormat);
-            var resultModel = (BlockHeaderModel)json.Value;
-
-            Assert.Null(resultModel);
+            Assert.IsType<NotFoundObjectResult>(this.controller.GetBlockHeader(hash, isJsonFormat));
         }
 
         [Fact]