Yes you can! Whether you just don’t like mayonnaise or want a low-fat alternative, yogurt is a great substitute for mayonnaise. It really is a personal choice whether you use a full cup of mayonnaise or a full cup of yogurt or even mix half yogurt and half mayonnaise. Greek yogurt is a lovely full cream substitute and if you have to factor in calories then opt for a fat free variety. Lactose free yogurts are wonderful to use for any friend or relative who suffers from dairy sensitivities. Yogurt definitely gives everything a much lighter feel and is not as rich and tangy as mayonnaise. Another good alternative would be sour cream but it will lack that element of sweetness provided by the mayonnaise.