diff --git a/src/NuGetLicense/CommandLineOptionsParser.cs b/src/NuGetLicense/CommandLineOptionsParser.cs
index 2ddc31f4..75887bcb 100644
--- a/src/NuGetLicense/CommandLineOptionsParser.cs
+++ b/src/NuGetLicense/CommandLineOptionsParser.cs
@@ -39,9 +39,14 @@ public string[] GetInputFiles(string? inputFile, string? inputJsonFile)
                 return [inputFile];
             }
 
-            return inputJsonFile != null
-                ? JsonSerializer.Deserialize<string[]>(_fileSystem.File.ReadAllText(inputJsonFile))!
-                : throw new ArgumentException("Please provide an input file using --input or --json-input");
+            if (inputJsonFile != null)
+            {
+                return JsonSerializer.Deserialize<string[]>(_fileSystem.File.ReadAllText(inputJsonFile))!;
+            }
+
+            // Defensive check: validation should already be done at command line parsing level,
+            // but throw exception if called directly or if validation is bypassed
+            throw new ArgumentException("Please provide an input file using --input or --json-input");
         }
 
         public string[] GetAllowedLicenses(string? allowedLicenses)
diff --git a/src/NuGetLicense/Program.cs b/src/NuGetLicense/Program.cs
index 3395f23b..14b1953a 100644
--- a/src/NuGetLicense/Program.cs
+++ b/src/NuGetLicense/Program.cs
@@ -119,10 +119,24 @@ public static RootCommand CreateRootCommand()
 
             rootCommand.SetAction(async (parseResult, cancellationToken) =>
             {
+                string? inputFile = parseResult.GetValue(inputFileOption);
+                string? inputJsonFile = parseResult.GetValue(inputJsonFileOption);
+
+                // Check if mandatory parameters are provided
+                if (inputFile == null && inputJsonFile == null)
+                {
+                    Console.Error.WriteLine("Error: Please provide an input file using --input or --json-input");
+                    Console.Error.WriteLine();
+                    // Show help by parsing and invoking with --help argument
+                    ParseResult helpResult = rootCommand.Parse(new[] { "--help" });
+                    await helpResult.InvokeAsync();
+                    return 1;
+                }
+
                 var options = new CommandLineOptions
                 {
-                    InputFile = parseResult.GetValue(inputFileOption),
-                    InputJsonFile = parseResult.GetValue(inputJsonFileOption),
+                    InputFile = inputFile,
+                    InputJsonFile = inputJsonFile,
                     IncludeTransitive = parseResult.GetValue(includeTransitiveOption),
                     AllowedLicenses = parseResult.GetValue(allowedLicensesOption),
                     IgnoredPackages = parseResult.GetValue(ignoredPackagesOption),