Place the cubed potatoes in a large pot and cover with water. Bring to a boil and cook until fork-tender, about 12–15 minutes.
Drain the potatoes well and let them cool slightly for about 10 minutes.
Transfer the warm potatoes to a large mixing bowl. Add the chopped eggs, onions, and pickles, gently stirring to combine.
Fold in the mayonnaise until the salad reaches your desired level of creaminess.
Stir in the mustard, then season with salt and pepper to taste.
Chill for at least 1 hour before serving for best flavor. Stir gently and adjust seasoning if needed before serving.
Enjoy!