diff --git a/changelogs/current.yaml b/changelogs/current.yaml
index feb4e2fd4398..981e449d60d3 100644
--- a/changelogs/current.yaml
+++ b/changelogs/current.yaml
@@ -14,6 +14,10 @@ bug_fixes:
 - area: happy_eyeballs
   change: |
     Validate that ``additional_address`` are IP addresses instead of crashing when sorting.
+- area: balsa
+  change: |
+    Fix incorrect handling of non-101 1xx responses. This fix can be temporarily reverted by setting runtime guard
+    ``envoy.reloadable_features.wait_for_first_byte_before_balsa_msg_done`` to false.
 
 removed_config_or_runtime:
 # *Normally occurs at the end of the* :ref:`deprecation period <deprecated>`
diff --git a/source/common/http/http1/balsa_parser.cc b/source/common/http/http1/balsa_parser.cc
index 5ffffd1de890..70493fc0ec4d 100644
--- a/source/common/http/http1/balsa_parser.cc
+++ b/source/common/http/http1/balsa_parser.cc
@@ -360,7 +360,10 @@ void BalsaParser::HeaderDone() {
 void BalsaParser::ContinueHeaderDone() {}
 
 void BalsaParser::MessageDone() {
-  if (status_ == ParserStatus::Error) {
+  if (status_ == ParserStatus::Error ||
+      // In the case of early 1xx, MessageDone() can be called twice in a row.
+      // The !first_byte_processed_ check is to make this function idempotent.
+      (wait_for_first_byte_before_msg_done_ && !first_byte_processed_)) {
     return;
   }
   status_ = convertResult(connection_->onMessageComplete());
diff --git a/source/common/http/http1/balsa_parser.h b/source/common/http/http1/balsa_parser.h
index 61a6e327b556..321dc0a01bfb 100644
--- a/source/common/http/http1/balsa_parser.h
+++ b/source/common/http/http1/balsa_parser.h
@@ -85,6 +85,9 @@ class BalsaParser : public Parser, public quiche::BalsaVisitorInterface {
   // Latched value of `envoy.reloadable_features.http1_balsa_delay_reset`.
   const bool delay_reset_ =
       Runtime::runtimeFeatureEnabled("envoy.reloadable_features.http1_balsa_delay_reset");
+  // Latched value of `envoy.reloadable_features.wait_for_first_byte_before_balsa_msg_done`.
+  const bool wait_for_first_byte_before_msg_done_ = Runtime::runtimeFeatureEnabled(
+      "envoy.reloadable_features.wait_for_first_byte_before_balsa_msg_done");
 };
 
 } // namespace Http1
diff --git a/source/common/runtime/runtime_features.cc b/source/common/runtime/runtime_features.cc
index babfb11c2a0a..b65b07ea86df 100644
--- a/source/common/runtime/runtime_features.cc
+++ b/source/common/runtime/runtime_features.cc
@@ -107,6 +107,7 @@ RUNTIME_GUARD(envoy_reloadable_features_use_typed_metadata_in_proxy_protocol_lis
 RUNTIME_GUARD(envoy_reloadable_features_validate_connect);
 RUNTIME_GUARD(envoy_reloadable_features_validate_grpc_header_before_log_grpc_status);
 RUNTIME_GUARD(envoy_reloadable_features_validate_upstream_headers);
+RUNTIME_GUARD(envoy_reloadable_features_wait_for_first_byte_before_balsa_msg_done);
 RUNTIME_GUARD(envoy_reloadable_features_xds_failover_to_primary_enabled);
 RUNTIME_GUARD(envoy_reloadable_features_xdstp_path_avoid_colon_encoding);
 RUNTIME_GUARD(envoy_restart_features_allow_client_socket_creation_failure);
diff --git a/test/integration/protocol_integration_test.cc b/test/integration/protocol_integration_test.cc
index 510cd6924d9c..58154161a6e6 100644
--- a/test/integration/protocol_integration_test.cc
+++ b/test/integration/protocol_integration_test.cc
@@ -1557,6 +1557,90 @@ TEST_P(ProtocolIntegrationTest, EnvoyProxying104) {
   testEnvoyProxying1xx(false, false, false, "104");
 }
 
+TEST_P(DownstreamProtocolIntegrationTest, EnvoyProxying102DelayBalsaReset) {
+  if (GetParam().http1_implementation != Http1ParserImpl::BalsaParser ||
+      GetParam().upstream_protocol != Http::CodecType::HTTP1 ||
+      GetParam().downstream_protocol != Http::CodecType::HTTP1) {
+    GTEST_SKIP() << "This test is only relevant for HTTP1 BalsaParser";
+  }
+  config_helper_.addConfigModifier(
+      [&](envoy::extensions::filters::network::http_connection_manager::v3::HttpConnectionManager&
+              hcm) -> void { hcm.set_proxy_100_continue(true); });
+  config_helper_.addRuntimeOverride(
+      "envoy.reloadable_features.wait_for_first_byte_before_balsa_msg_done", "false");
+  config_helper_.addRuntimeOverride("envoy.reloadable_features.http1_balsa_delay_reset", "true");
+  initialize();
+
+  codec_client_ = makeHttpConnection(lookupPort("http"));
+  auto response = codec_client_->makeHeaderOnlyRequest(
+      Http::TestRequestHeaderMapImpl{{":method", "HEAD"},
+                                     {":path", "/dynamo/url"},
+                                     {":scheme", "http"},
+                                     {":authority", "sni.lyft.com"},
+                                     {"expect", "100-contINUE"}});
+  waitForNextUpstreamRequest();
+  upstream_request_->encode1xxHeaders(Http::TestResponseHeaderMapImpl{{":status", "102"}});
+  response->waitFor1xxHeaders();
+  upstream_request_->encodeHeaders(default_response_headers_, true);
+
+  EXPECT_FALSE(response->waitForEndStream());
+
+  cleanupUpstreamAndDownstream();
+}
+
+TEST_P(DownstreamProtocolIntegrationTest, EnvoyProxying102DelayBalsaResetWaitForFirstByte) {
+  if (GetParam().http1_implementation != Http1ParserImpl::BalsaParser ||
+      GetParam().upstream_protocol != Http::CodecType::HTTP1) {
+    GTEST_SKIP() << "This test is only relevant for HTTP1 upstream with BalsaParser";
+  }
+  config_helper_.addConfigModifier(
+      [&](envoy::extensions::filters::network::http_connection_manager::v3::HttpConnectionManager&
+              hcm) -> void { hcm.set_proxy_100_continue(true); });
+  config_helper_.addRuntimeOverride(
+      "envoy.reloadable_features.wait_for_first_byte_before_balsa_msg_done", "true");
+  config_helper_.addRuntimeOverride("envoy.reloadable_features.http1_balsa_delay_reset", "true");
+  initialize();
+
+  codec_client_ = makeHttpConnection(lookupPort("http"));
+  auto response = codec_client_->makeHeaderOnlyRequest(
+      Http::TestRequestHeaderMapImpl{{":method", "HEAD"},
+                                     {":path", "/dynamo/url"},
+                                     {":scheme", "http"},
+                                     {":authority", "sni.lyft.com"},
+                                     {"expect", "100-contINUE"}});
+  waitForNextUpstreamRequest();
+  upstream_request_->encode1xxHeaders(Http::TestResponseHeaderMapImpl{{":status", "102"}});
+  response->waitFor1xxHeaders();
+  upstream_request_->encodeHeaders(default_response_headers_, true);
+  ASSERT_TRUE(response->waitForEndStream());
+}
+
+TEST_P(DownstreamProtocolIntegrationTest, EnvoyProxying102NoDelayBalsaReset) {
+  if (GetParam().http1_implementation != Http1ParserImpl::BalsaParser ||
+      GetParam().upstream_protocol != Http::CodecType::HTTP1) {
+    GTEST_SKIP() << "This test is only relevant for HTTP1 upstream with BalsaParser";
+  }
+  config_helper_.addConfigModifier(
+      [&](envoy::extensions::filters::network::http_connection_manager::v3::HttpConnectionManager&
+              hcm) -> void { hcm.set_proxy_100_continue(true); });
+  config_helper_.addRuntimeOverride("envoy.reloadable_features.http1_balsa_delay_reset", "false");
+  initialize();
+
+  codec_client_ = makeHttpConnection(lookupPort("http"));
+  auto response = codec_client_->makeHeaderOnlyRequest(
+      Http::TestRequestHeaderMapImpl{{":method", "HEAD"},
+                                     {":path", "/dynamo/url"},
+                                     {":scheme", "http"},
+                                     {":authority", "sni.lyft.com"},
+                                     {"expect", "100-contINUE"}});
+
+  waitForNextUpstreamRequest();
+  upstream_request_->encode1xxHeaders(Http::TestResponseHeaderMapImpl{{":status", "102"}});
+  response->waitFor1xxHeaders();
+  upstream_request_->encodeHeaders(default_response_headers_, true);
+  ASSERT_TRUE(response->waitForEndStream());
+}
+
 TEST_P(ProtocolIntegrationTest, TwoRequests) { testTwoRequests(); }
 
 TEST_P(ProtocolIntegrationTest, TwoRequestsWithForcedBackup) { testTwoRequests(true); }