Gather all ingredients and ensure your vegetables are prepped.
In a large mixing bowl, combine the diced ham and thawed peas.
Add the diced celery and pineapple to the bowl.
In a small bowl, mix together the mayonnaise and Dijon mustard.
Pour the mayonnaise mixture over the ham and vegetables.
Gently fold the ingredients together until well combined.
Season with salt and pepper to taste.
If using, add chopped parsley for freshness.
Cover the bowl and refrigerate for at least 30 minutes before serving.
Serve chilled on a bed of lettuce or as a sandwich filling.