diff --git a/eng/pipelines/common/templates/browser-wasm-build-tests.yml b/eng/pipelines/common/templates/browser-wasm-build-tests.yml
index 39fca50137411f..224f2887801083 100644
--- a/eng/pipelines/common/templates/browser-wasm-build-tests.yml
+++ b/eng/pipelines/common/templates/browser-wasm-build-tests.yml
@@ -125,6 +125,11 @@ jobs:
             parameters:
               creator: dotnet-bot
               testRunNamePrefixSuffix: Mono_$(_BuildConfig)_$(_hostedOs)
-              extraHelixArguments: /p:BrowserHost=$(_hostedOs)
+              # WBT (buildwasmapps) fans out into several sendtohelixhelp.proj invocations
+              # (Workloads/Webcil/Fingerprinting/Bundler combos). sendtohelix.proj already builds
+              # them with BuildInParallel=true, but that only parallelizes when the msbuild running
+              # it has multiple nodes. /maxcpucount lets the Helix jobs be sent (and waited on)
+              # concurrently instead of one-send-then-wait-for-completion serially (see issue #118938).
+              extraHelixArguments: /p:BrowserHost=$(_hostedOs) /maxcpucount:8
               scenarios:
               - buildwasmapps
diff --git a/eng/pipelines/common/templates/browser-wasm-coreclr-build-tests.yml b/eng/pipelines/common/templates/browser-wasm-coreclr-build-tests.yml
index ac76b6332c3801..635d669e05af92 100644
--- a/eng/pipelines/common/templates/browser-wasm-coreclr-build-tests.yml
+++ b/eng/pipelines/common/templates/browser-wasm-coreclr-build-tests.yml
@@ -138,6 +138,11 @@ jobs:
             parameters:
               creator: dotnet-bot
               testRunNamePrefixSuffix: CoreCLR_$(_BuildConfig)_$(_hostedOs)
-              extraHelixArguments: /p:BrowserHost=$(_hostedOs)
+              # WBT (buildwasmapps) fans out into several sendtohelixhelp.proj invocations
+              # (Workloads/Webcil/Fingerprinting/Bundler combos). sendtohelix.proj already builds
+              # them with BuildInParallel=true, but that only parallelizes when the msbuild running
+              # it has multiple nodes. /maxcpucount lets the Helix jobs be sent (and waited on)
+              # concurrently instead of one-send-then-wait-for-completion serially (see issue #118938).
+              extraHelixArguments: /p:BrowserHost=$(_hostedOs) /maxcpucount:8
               scenarios:
               - buildwasmapps
diff --git a/eng/pipelines/common/templates/simple-wasm-build-tests.yml b/eng/pipelines/common/templates/simple-wasm-build-tests.yml
index ec0678f6463e4b..dd7ab4e3e2a99e 100644
--- a/eng/pipelines/common/templates/simple-wasm-build-tests.yml
+++ b/eng/pipelines/common/templates/simple-wasm-build-tests.yml
@@ -47,7 +47,12 @@ jobs:
           parameters:
             creator: dotnet-bot
             testRunNamePrefixSuffix: Mono_$(_BuildConfig)_$(_hostedOs)
-            extraHelixArguments: /p:BrowserHost=$(_hostedOs)
+            # WBT (buildwasmapps) fans out into several sendtohelixhelp.proj invocations
+            # (Workloads/Webcil/Fingerprinting/Bundler combos). sendtohelix.proj already builds
+            # them with BuildInParallel=true, but that only parallelizes when the msbuild running
+            # it has multiple nodes. /maxcpucount lets the Helix jobs be sent (and waited on)
+            # concurrently instead of one-send-then-wait-for-completion serially (see issue #118938).
+            extraHelixArguments: /p:BrowserHost=$(_hostedOs) /maxcpucount:8
             scenarios:
             - buildwasmapps