diff --git a/packages/opentelemetry-core/src/context/propagation/B3Propagator.ts b/packages/opentelemetry-core/src/context/propagation/B3Propagator.ts
index 9a6f38f67d..27689c5de9 100644
--- a/packages/opentelemetry-core/src/context/propagation/B3Propagator.ts
+++ b/packages/opentelemetry-core/src/context/propagation/B3Propagator.ts
@@ -26,7 +26,7 @@ import { getParentSpanContext, setExtractedSpanContext } from '../context';
 export const X_B3_TRACE_ID = 'x-b3-traceid';
 export const X_B3_SPAN_ID = 'x-b3-spanid';
 export const X_B3_SAMPLED = 'x-b3-sampled';
-const VALID_TRACEID_REGEX = /^[0-9a-f]{32}$/i;
+const VALID_TRACEID_REGEX = /^([0-9a-f]{16}){1,2}$/i;
 const VALID_SPANID_REGEX = /^[0-9a-f]{16}$/i;
 const INVALID_ID_REGEX = /^0+$/i;
 
@@ -72,16 +72,21 @@ export class B3Propagator implements HttpTextPropagator {
     const traceIdHeader = getter(carrier, X_B3_TRACE_ID);
     const spanIdHeader = getter(carrier, X_B3_SPAN_ID);
     const sampledHeader = getter(carrier, X_B3_SAMPLED);
-    const traceId = Array.isArray(traceIdHeader)
+
+    const traceIdHeaderValue = Array.isArray(traceIdHeader)
       ? traceIdHeader[0]
       : traceIdHeader;
     const spanId = Array.isArray(spanIdHeader) ? spanIdHeader[0] : spanIdHeader;
+
     const options = Array.isArray(sampledHeader)
       ? sampledHeader[0]
       : sampledHeader;
 
-    if (typeof traceId !== 'string' || typeof spanId !== 'string')
+    if (typeof traceIdHeaderValue !== 'string' || typeof spanId !== 'string') {
       return context;
+    }
+
+    const traceId = traceIdHeaderValue.padStart(32, '0');
 
     if (isValidTraceId(traceId) && isValidSpanId(spanId)) {
       return setExtractedSpanContext(context, {
diff --git a/packages/opentelemetry-core/test/context/B3Propagator.test.ts b/packages/opentelemetry-core/test/context/B3Propagator.test.ts
index f403bc72a0..7b779c3b94 100644
--- a/packages/opentelemetry-core/test/context/B3Propagator.test.ts
+++ b/packages/opentelemetry-core/test/context/B3Propagator.test.ts
@@ -289,5 +289,21 @@ describe('B3Propagator', () => {
       assert.ok(ctx2 === Context.ROOT_CONTEXT);
       assert.ok(ctx3 === Context.ROOT_CONTEXT);
     });
+
+    it('should left-pad 64 bit trace ids with 0', () => {
+      carrier[X_B3_TRACE_ID] = '8448eb211c80319c';
+      carrier[X_B3_SPAN_ID] = 'b7ad6b7169203331';
+      carrier[X_B3_SAMPLED] = '1';
+      const extractedSpanContext = getExtractedSpanContext(
+        b3Propagator.extract(Context.ROOT_CONTEXT, carrier, defaultGetter)
+      );
+
+      assert.deepStrictEqual(extractedSpanContext, {
+        spanId: 'b7ad6b7169203331',
+        traceId: '00000000000000008448eb211c80319c',
+        isRemote: true,
+        traceFlags: TraceFlags.SAMPLED,
+      });
+    });
   });
 });