diff --git a/CHANGELOG.md b/CHANGELOG.md
index c399e74acfa..394ba4e4365 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,6 +2,12 @@
 
 ## Unreleased
 
+### SDK
+
+#### Exporters
+
+* OTLP: Fix sign extension of `LogRecord` flags in the low-allocation log marshaler
+
 ## Version 1.63.0 (2026-06-05)
 
 ### API
diff --git a/exporters/otlp/common/src/main/java/io/opentelemetry/exporter/internal/otlp/logs/LogStatelessMarshaler.java b/exporters/otlp/common/src/main/java/io/opentelemetry/exporter/internal/otlp/logs/LogStatelessMarshaler.java
index fd8e69a63c8..340842664ad 100644
--- a/exporters/otlp/common/src/main/java/io/opentelemetry/exporter/internal/otlp/logs/LogStatelessMarshaler.java
+++ b/exporters/otlp/common/src/main/java/io/opentelemetry/exporter/internal/otlp/logs/LogStatelessMarshaler.java
@@ -52,7 +52,7 @@ public void writeTo(Serializer output, LogRecordData log, MarshalerContext conte
         log.getTotalAttributeCount() - log.getAttributes().size());
 
     SpanContext spanContext = log.getSpanContext();
-    output.serializeFixed32(LogRecord.FLAGS, spanContext.getTraceFlags().asByte());
+    output.serializeByteAsFixed32(LogRecord.FLAGS, spanContext.getTraceFlags().asByte());
     if (!spanContext.getTraceId().equals(INVALID_TRACE_ID)) {
       output.serializeTraceId(LogRecord.TRACE_ID, spanContext.getTraceId(), context);
     }
@@ -91,7 +91,7 @@ public int getBinarySerializedSize(LogRecordData log, MarshalerContext context)
     size += MarshalerUtil.sizeUInt32(LogRecord.DROPPED_ATTRIBUTES_COUNT, droppedAttributesCount);
 
     SpanContext spanContext = log.getSpanContext();
-    size += MarshalerUtil.sizeFixed32(LogRecord.FLAGS, spanContext.getTraceFlags().asByte());
+    size += MarshalerUtil.sizeByteAsFixed32(LogRecord.FLAGS, spanContext.getTraceFlags().asByte());
     if (!spanContext.getTraceId().equals(INVALID_TRACE_ID)) {
       size += MarshalerUtil.sizeTraceId(LogRecord.TRACE_ID, spanContext.getTraceId());
     }
diff --git a/exporters/otlp/common/src/test/java/io/opentelemetry/exporter/internal/otlp/logs/LowAllocationLogRequestMarshalerTest.java b/exporters/otlp/common/src/test/java/io/opentelemetry/exporter/internal/otlp/logs/LowAllocationLogRequestMarshalerTest.java
index 8b86a907b64..fe2bed86f5e 100644
--- a/exporters/otlp/common/src/test/java/io/opentelemetry/exporter/internal/otlp/logs/LowAllocationLogRequestMarshalerTest.java
+++ b/exporters/otlp/common/src/test/java/io/opentelemetry/exporter/internal/otlp/logs/LowAllocationLogRequestMarshalerTest.java
@@ -69,8 +69,12 @@ class LowAllocationLogRequestMarshalerTest {
       InstrumentationScopeInfo.create("name");
   private static final String TRACE_ID = "7b2e170db4df2d593ddb4ddf2ddf2d59";
   private static final String SPAN_ID = "170d3ddb4d23e81f";
+  // Use a trace flags value with the high bit set (0x80) so the relative comparisons below catch
+  // sign extension of the byte flags into the OTLP fixed32 field. With a low value like 0x01 the
+  // sign-extension bug would be hidden.
   private static final SpanContext SPAN_CONTEXT =
-      SpanContext.create(TRACE_ID, SPAN_ID, TraceFlags.getSampled(), TraceState.getDefault());
+      SpanContext.create(
+          TRACE_ID, SPAN_ID, TraceFlags.fromByte((byte) 0x80), TraceState.getDefault());
 
   private final List<LogRecordData> logRecordDataList = createLogRecordDataList();