diff --git a/nebula-logger/core/main/logger-engine/classes/LogEntryEventBuilder.cls b/nebula-logger/core/main/logger-engine/classes/LogEntryEventBuilder.cls
index ef5a8f332..3a963f3f0 100644
--- a/nebula-logger/core/main/logger-engine/classes/LogEntryEventBuilder.cls
+++ b/nebula-logger/core/main/logger-engine/classes/LogEntryEventBuilder.cls
@@ -32,6 +32,10 @@ global with sharing class LogEntryEventBuilder {
 
   @TestVisible
   private String debugMessage = '';
+
+  @TestVisible
+  private static Boolean isApexSystemDebugSupportedOverride = true; // default to true for backwards compatibility with existing tests
+
   private Boolean detailsAreSet = false;
   private Boolean shouldSave;
   private Set<String> tags = new Set<String>();
@@ -774,8 +778,10 @@ global with sharing class LogEntryEventBuilder {
       try {
         this.logEntryEvent.put(field, value);
       } catch (System.Exception ex) {
-        LogMessage logMessage = new LogMessage('Could not set field {0} with value {1}', field, value);
-        System.debug(System.LoggingLevel.WARN, logMessage.getMessage());
+        if (isApexSystemDebugSupported()) {
+          LogMessage logMessage = new LogMessage('Could not set field {0} with value {1}', field, value);
+          System.debug(System.LoggingLevel.WARN, logMessage.getMessage());
+        }
       }
     }
 
@@ -922,7 +928,7 @@ global with sharing class LogEntryEventBuilder {
 
   @SuppressWarnings('PMD.AvoidDebugStatements')
   private void logToApexDebug(String message) {
-    if (this.userSettings.IsApexSystemDebugLoggingEnabled__c == false) {
+    if (this.userSettings.IsApexSystemDebugLoggingEnabled__c == false || isApexSystemDebugSupported() == false) {
       return;
     }
 
@@ -1340,6 +1346,17 @@ global with sharing class LogEntryEventBuilder {
     return securityDecision.getRecords();
   }
 
+  /**
+   * @description Returns whether Apex System.debug() is supported, supports an override for testing purposes.
+   * @return   `Boolean`   true if Apex System.debug() is supported, false otherwise
+   */
+  private static Boolean isApexSystemDebugSupported() {
+    if (System.Test.isRunningTest()) {
+      return isApexSystemDebugSupportedOverride;
+    }
+    return String.isBlank(NAMESPACE_PREFIX);
+  }
+
   @SuppressWarnings('PMD.ApexDoc')
   public class LoggingContext {
     public String currentEntryScenario;
diff --git a/nebula-logger/core/tests/logger-engine/classes/LogEntryEventBuilder_Tests.cls b/nebula-logger/core/tests/logger-engine/classes/LogEntryEventBuilder_Tests.cls
index 1c9ad3387..8b234c9b3 100644
--- a/nebula-logger/core/tests/logger-engine/classes/LogEntryEventBuilder_Tests.cls
+++ b/nebula-logger/core/tests/logger-engine/classes/LogEntryEventBuilder_Tests.cls
@@ -2496,6 +2496,44 @@ private class LogEntryEventBuilder_Tests {
     System.Assert.isNull(builder.getLogEntryEvent().get(datetimeField));
   }
 
+  @IsTest
+  static void it_should_skip_apex_system_debug_when_not_supported() {
+    Test.startTest();
+    LogEntryEventBuilder.isApexSystemDebugSupportedOverride = false;
+    DebugStringExample example = new DebugStringExample();
+    LoggerSettings__c userSettings = getUserSettings();
+    userSettings.IsApexSystemDebugLoggingEnabled__c = true;
+    LogEntryEventBuilder builder = example.myMethod(userSettings);
+    Test.stopTest();
+
+    System.Assert.areEqual(
+      '',
+      builder.debugMessage,
+      'Debug message should be empty when Apex System.debug() is not supported, ie: executed in Managed Package context'
+    );
+    System.Assert.areEqual(example.loggingString, builder.getLogEntryEvent().Message__c, 'Message should be set on the log entry event');
+  }
+
+  @IsTest
+  static void it_should_use_apex_system_debug_when_supported() {
+    Test.startTest();
+    LoggerParameter.setMock(
+      new LoggerParameter__mdt(DeveloperName = 'SystemDebugMessageFormat', Value__c = '{OriginLocation__c}\n{Message__c}: {LoggingLevel__c}')
+    );
+
+    DebugStringExample example = new DebugStringExample();
+    LoggerSettings__c userSettings = getUserSettings();
+    userSettings.IsApexSystemDebugLoggingEnabled__c = true;
+    LogEntryEventBuilder builder = example.myMethod(userSettings);
+    Test.stopTest();
+
+    System.Assert.areEqual(
+      DebugStringExample.class.getName() + '.myMethod' + '\n' + example.loggingString + ': ' + System.LoggingLevel.DEBUG.name(),
+      builder.debugMessage,
+      'Debug message should be set when Apex System.debug() is supported, ie: executed in Unmanaged Package context and IsApexSystemDebugLoggingEnabled__c is true'
+    );
+  }
+
   @IsTest
   static void it_should_use_configured_log_entry_event_fields_for_debug_string() {
     // Don't bother testing stack trace logic when using a namespace prefix - there are