diff --git a/experimental/CHANGELOG.md b/experimental/CHANGELOG.md
index a45f89af66..0fa4a148e4 100644
--- a/experimental/CHANGELOG.md
+++ b/experimental/CHANGELOG.md
@@ -19,6 +19,7 @@ All notable changes to experimental packages in this project will be documented
 * fix(instrumentation): only call `onRequire` for full matches on core modules with sub-paths [#3451](https://github.com/open-telemetry/opentelemetry-js/pull/3451) @mhassan1
 * fix(instrumentation): add back support for absolute paths via `require-in-the-middle` [#3457](https://github.com/open-telemetry/opentelemetry-js/pull/3457) @mhassan1
 * fix(prometheus-sanitization): replace repeated `_` with a single `_` [3470](https://github.com/open-telemetry/opentelemetry-js/pull/3470) @samimusallam
+* fix(prometheus-serializer): correct string used for NaN [#3477](https://github.com/open-telemetry/opentelemetry-js/pull/3477) @JacksonWeber
 
 ### :books: (Refine Doc)
 
diff --git a/experimental/packages/opentelemetry-exporter-prometheus/src/PrometheusSerializer.ts b/experimental/packages/opentelemetry-exporter-prometheus/src/PrometheusSerializer.ts
index 54152a4920..2d9808bf35 100644
--- a/experimental/packages/opentelemetry-exporter-prometheus/src/PrometheusSerializer.ts
+++ b/experimental/packages/opentelemetry-exporter-prometheus/src/PrometheusSerializer.ts
@@ -106,7 +106,7 @@ function enforcePrometheusNamingConvention(
 
 function valueString(value: number) {
   if (Number.isNaN(value)) {
-    return 'Nan';
+    return 'NaN';
   } else if (!Number.isFinite(value)) {
     if (value < 0) {
       return '-Inf';
diff --git a/experimental/packages/opentelemetry-exporter-prometheus/test/PrometheusSerializer.test.ts b/experimental/packages/opentelemetry-exporter-prometheus/test/PrometheusSerializer.test.ts
index 6c5def7bcf..5495ca0a8b 100644
--- a/experimental/packages/opentelemetry-exporter-prometheus/test/PrometheusSerializer.test.ts
+++ b/experimental/packages/opentelemetry-exporter-prometheus/test/PrometheusSerializer.test.ts
@@ -622,7 +622,7 @@ describe('PrometheusSerializer', () => {
     it('should serialize non-finite values', async () => {
       const serializer = new PrometheusSerializer();
       const cases = [
-        [NaN, 'Nan'],
+        [NaN, 'NaN'],
         [-Infinity, '-Inf'],
         [+Infinity, '+Inf'],
       ] as [number, string][];