diff --git a/slack-api-client/src/main/java/com/slack/api/methods/RequestFormBuilder.java b/slack-api-client/src/main/java/com/slack/api/methods/RequestFormBuilder.java
index 57b3c1851..bf2cf7a43 100644
--- a/slack-api-client/src/main/java/com/slack/api/methods/RequestFormBuilder.java
+++ b/slack-api-client/src/main/java/com/slack/api/methods/RequestFormBuilder.java
@@ -2317,6 +2317,14 @@ public static FormBody.Builder toForm(FilesCompleteUploadExternalRequest req) {
         }
         setIfNotNull("initial_comment", req.getInitialComment(), form);
         setIfNotNull("thread_ts", req.getThreadTs(), form);
+        if (req.getBlocksAsString() != null) {
+            form.add("blocks", req.getBlocksAsString());
+        } else if (req.getBlocks() != null) {
+            form.add("blocks", getJsonWithGsonAnonymInnerClassHandling(req.getBlocks()));
+        }
+        if (req.getBlocksAsString() != null && req.getBlocks() != null) {
+            log.warn("Although you set both blocksAsString and blocks, only blocksAsString was used.");
+        }
         return form;
     }
 
diff --git a/slack-api-client/src/main/java/com/slack/api/methods/impl/FilesUploadV2Helper.java b/slack-api-client/src/main/java/com/slack/api/methods/impl/FilesUploadV2Helper.java
index 7c805c9b5..b1ba227cd 100644
--- a/slack-api-client/src/main/java/com/slack/api/methods/impl/FilesUploadV2Helper.java
+++ b/slack-api-client/src/main/java/com/slack/api/methods/impl/FilesUploadV2Helper.java
@@ -97,6 +97,8 @@ public FilesUploadV2Response completeUploads(
                 .channels(v2Request.getChannels())
                 .initialComment(v2Request.getInitialComment())
                 .threadTs(v2Request.getThreadTs())
+                .blocks(v2Request.getBlocks())
+                .blocksAsString(v2Request.getBlocksAsString())
         );
         underlyingException.setCompleteResponse(response);
         if (!response.isOk()) {
diff --git a/slack-api-client/src/main/java/com/slack/api/methods/request/files/FilesCompleteUploadExternalRequest.java b/slack-api-client/src/main/java/com/slack/api/methods/request/files/FilesCompleteUploadExternalRequest.java
index 837cd4c6b..fa00c142b 100644
--- a/slack-api-client/src/main/java/com/slack/api/methods/request/files/FilesCompleteUploadExternalRequest.java
+++ b/slack-api-client/src/main/java/com/slack/api/methods/request/files/FilesCompleteUploadExternalRequest.java
@@ -1,6 +1,7 @@
 package com.slack.api.methods.request.files;
 
 import com.slack.api.methods.SlackApiRequest;
+import com.slack.api.model.block.LayoutBlock;
 import lombok.AllArgsConstructor;
 import lombok.Builder;
 import lombok.Data;
@@ -46,6 +47,18 @@ public class FilesCompleteUploadExternalRequest implements SlackApiRequest {
      */
     private String threadTs;
 
+    /**
+     * A JSON-based array of structured blocks, presented as a URL-encoded string.
+     * If initialComment is provided, this field is ignored.
+     */
+    private List<LayoutBlock> blocks;
+
+    /**
+     * A JSON-based array of structured blocks as a String, presented as a URL-encoded string.
+     * If initialComment is provided, this field is ignored.
+     */
+    private String blocksAsString;
+
     @Data
     @Builder
     @NoArgsConstructor
diff --git a/slack-api-client/src/main/java/com/slack/api/methods/request/files/FilesUploadV2Request.java b/slack-api-client/src/main/java/com/slack/api/methods/request/files/FilesUploadV2Request.java
index 33be36995..c4e41de0f 100644
--- a/slack-api-client/src/main/java/com/slack/api/methods/request/files/FilesUploadV2Request.java
+++ b/slack-api-client/src/main/java/com/slack/api/methods/request/files/FilesUploadV2Request.java
@@ -1,6 +1,7 @@
 package com.slack.api.methods.request.files;
 
 import com.slack.api.methods.SlackApiRequest;
+import com.slack.api.model.block.LayoutBlock;
 import lombok.AllArgsConstructor;
 import lombok.Builder;
 import lombok.Data;
@@ -150,4 +151,16 @@ public static class UploadFile {
      */
     private String threadTs;
 
+    /**
+     * A JSON-based array of structured blocks, presented as a URL-encoded string.
+     * If initialComment is provided, this field is ignored.
+     */
+    private List<LayoutBlock> blocks;
+
+    /**
+     * A JSON-based array of structured blocks as a String, presented as a URL-encoded string.
+     * If initialComment is provided, this field is ignored.
+     */
+    private String blocksAsString;
+
 }
diff --git a/slack-api-client/src/test/java/test_locally/api/methods/FilesUploadV2HelperTest.java b/slack-api-client/src/test/java/test_locally/api/methods/FilesUploadV2HelperTest.java
new file mode 100644
index 000000000..84a4d35f0
--- /dev/null
+++ b/slack-api-client/src/test/java/test_locally/api/methods/FilesUploadV2HelperTest.java
@@ -0,0 +1,57 @@
+package test_locally.api.methods;
+
+import com.slack.api.RequestConfigurator;
+import com.slack.api.methods.MethodsClient;
+import com.slack.api.methods.impl.FilesUploadV2Helper;
+import com.slack.api.methods.request.files.FilesCompleteUploadExternalRequest;
+import com.slack.api.methods.request.files.FilesUploadV2Request;
+import com.slack.api.methods.response.files.FilesCompleteUploadExternalResponse;
+import com.slack.api.model.block.LayoutBlock;
+import com.slack.api.model.block.SectionBlock;
+import com.slack.api.util.http.SlackHttpClient;
+import okhttp3.OkHttpClient;
+import org.junit.Test;
+import org.mockito.ArgumentCaptor;
+
+import java.util.Collections;
+import java.util.List;
+
+import static org.hamcrest.CoreMatchers.is;
+import static org.hamcrest.MatcherAssert.assertThat;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.when;
+
+public class FilesUploadV2HelperTest {
+
+    @Test
+    @SuppressWarnings("unchecked")
+    public void completeUploadsPropagatesBlocks() throws Exception {
+        // GIVEN
+        MethodsClient client = mock(MethodsClient.class);
+        when(client.getSlackHttpClient()).thenReturn(new SlackHttpClient(new OkHttpClient()));
+
+        FilesCompleteUploadExternalResponse response = new FilesCompleteUploadExternalResponse();
+        response.setOk(true);
+        response.setFiles(Collections.emptyList());
+
+        ArgumentCaptor<RequestConfigurator<FilesCompleteUploadExternalRequest.FilesCompleteUploadExternalRequestBuilder>> captor =
+                ArgumentCaptor.forClass(RequestConfigurator.class);
+        when(client.filesCompleteUploadExternal(captor.capture())).thenReturn(response);
+
+        List<LayoutBlock> blocks = Collections.<LayoutBlock>singletonList(SectionBlock.builder().build());
+        FilesUploadV2Request request = FilesUploadV2Request.builder()
+                .blocks(blocks)
+                .blocksAsString("[]")
+                .build();
+
+        // WHEN
+        new FilesUploadV2Helper(client).completeUploads(request, Collections.emptyList());
+
+        // THEN
+        FilesCompleteUploadExternalRequest completeRequest = captor.getValue()
+                .configure(FilesCompleteUploadExternalRequest.builder())
+                .build();
+        assertThat(completeRequest.getBlocks(), is(blocks));
+        assertThat(completeRequest.getBlocksAsString(), is("[]"));
+    }
+}
diff --git a/slack-api-client/src/test/java/test_locally/api/methods/RequestFormBuilderTest.java b/slack-api-client/src/test/java/test_locally/api/methods/RequestFormBuilderTest.java
index b25732f63..3b54c8187 100644
--- a/slack-api-client/src/test/java/test_locally/api/methods/RequestFormBuilderTest.java
+++ b/slack-api-client/src/test/java/test_locally/api/methods/RequestFormBuilderTest.java
@@ -4,6 +4,7 @@
 import com.slack.api.methods.request.calls.CallsAddRequest;
 import com.slack.api.methods.request.chat.ChatPostMessageRequest;
 import com.slack.api.methods.request.chat.ChatUnfurlRequest;
+import com.slack.api.methods.request.files.FilesCompleteUploadExternalRequest;
 import com.slack.api.model.Attachment;
 import com.slack.api.model.CallParticipant;
 import com.slack.api.model.block.LayoutBlock;
@@ -60,6 +61,43 @@ public void testEmptyListJsonSerialization() {
         assertThat(form.value(blocksIndexInForm), is("[]"));
     }
 
+    @Test
+    public void testFilesCompleteUploadExternalBlocksJsonSerialization() {
+        // GIVEN
+        List<LayoutBlock> blocks = new ArrayList<>();
+        blocks.add(MyTestBlock.builder().build());
+
+        FilesCompleteUploadExternalRequest request = FilesCompleteUploadExternalRequest.builder()
+                .blocks(blocks)
+                .build();
+
+        // WHEN
+        FormBody form = RequestFormBuilder.toForm(request).build();
+
+        // THEN
+        assertThat(form.name(0), is("blocks"));
+        assertThat(form.value(0), is("[{\"type\":\"myTestBlock\"}]"));
+    }
+
+    @Test
+    public void testFilesCompleteUploadExternalBlocksAsStringTakesPrecedence() {
+        // GIVEN
+        List<LayoutBlock> blocks = new ArrayList<>();
+        blocks.add(MyTestBlock.builder().build());
+
+        FilesCompleteUploadExternalRequest request = FilesCompleteUploadExternalRequest.builder()
+                .blocks(blocks)
+                .blocksAsString("[]")
+                .build();
+
+        // WHEN
+        FormBody form = RequestFormBuilder.toForm(request).build();
+
+        // THEN
+        assertThat(form.name(0), is("blocks"));
+        assertThat(form.value(0), is("[]"));
+    }
+
     @Test
     public void testBlocksJsonSerializationWithInnerClassInit() {
         // GIVEN