diff --git a/java/google/registry/flows/EppController.java b/java/google/registry/flows/EppController.java
index 38594124f..98782fd05 100644
--- a/java/google/registry/flows/EppController.java
+++ b/java/google/registry/flows/EppController.java
@@ -14,11 +14,16 @@
 
 package google.registry.flows;
 
+import static com.google.common.base.Strings.nullToEmpty;
+import static com.google.common.io.BaseEncoding.base64;
 import static google.registry.flows.EppXmlTransformer.unmarshal;
+import static java.nio.charset.StandardCharsets.UTF_8;
 
 import com.google.common.annotations.VisibleForTesting;
 import com.google.common.base.Joiner;
 import com.google.common.base.Optional;
+import com.google.common.base.Strings;
+import com.google.common.collect.ImmutableMap;
 import google.registry.flows.FlowModule.EppExceptionInProviderException;
 import google.registry.model.eppcommon.Trid;
 import google.registry.model.eppinput.EppInput;
@@ -30,6 +35,7 @@ import google.registry.monitoring.whitebox.BigQueryMetricsEnqueuer;
 import google.registry.monitoring.whitebox.EppMetric;
 import google.registry.util.FormattingLogger;
 import javax.inject.Inject;
+import org.json.simple.JSONValue;
 
 /**
  * An implementation of the EPP command/response protocol.
@@ -46,7 +52,7 @@ public final class EppController {
   @Inject BigQueryMetricsEnqueuer bigQueryMetricsEnqueuer;
   @Inject EppController() {}
 
-  /** Read EPP XML, execute the matching flow, and return an {@link EppOutput}. */
+  /** Reads EPP XML, executes the matching flow, and returns an {@link EppOutput}. */
   public EppOutput handleEppCommand(
       SessionMetadata sessionMetadata,
       TransportCredentials credentials,
@@ -61,7 +67,21 @@ public final class EppController {
       try {
         eppInput = unmarshal(EppInput.class, inputXmlBytes);
       } catch (EppException e) {
-        // Send the client an error message, with no clTRID since we couldn't unmarshal it.
+        // Log the unmarshalling error, with the raw bytes (in base64) to help with debugging.
+        logger.infofmt(
+            e,
+            "EPP request XML unmarshalling failed - \"%s\":\n%s\n%s\n%s\n%s",
+            e.getMessage(),
+            JSONValue.toJSONString(
+                ImmutableMap.<String, Object>of(
+                    "clientId", nullToEmpty(sessionMetadata.getClientId()),
+                    "resultCode", e.getResult().getCode().code,
+                    "resultMessage", e.getResult().getCode().msg,
+                    "xmlBytes", base64().encode(inputXmlBytes))),
+            Strings.repeat("=", 40),
+            new String(inputXmlBytes, UTF_8).trim(), // Charset decoding failures are swallowed.
+            Strings.repeat("=", 40));
+        // Return early by sending an error message, with no clTRID since we couldn't unmarshal it.
         metricBuilder.setStatus(e.getResult().getCode());
         return getErrorResponse(e.getResult(), Trid.create(null));
       }
@@ -92,7 +112,7 @@ public final class EppController {
     }
   }
 
-  /** Run an EPP flow and convert known exceptions into EPP error responses. */
+  /** Runs an EPP flow and converts known exceptions into EPP error responses. */
   private EppOutput runFlowConvertEppErrors(FlowComponent flowComponent) {
     try {
       return flowComponent.flowRunner().run();
@@ -107,7 +127,7 @@ public final class EppController {
     }
   }
 
-  /** Create a response indicating an EPP failure. */
+  /** Creates a response indicating an EPP failure. */
   @VisibleForTesting
   static EppOutput getErrorResponse(Result result, Trid trid) {
     return EppOutput.create(new EppResponse.Builder()