The function of a facial moisturiser or any regular skin moisturiser is to keep your natural moisture close to your skin, and doing this at night would be good for anyone with a dry or normal skin type. If you have acne prone skin, however, this may be a bad idea. It all depends on how you apply the moisturiser and the specific kind you are using.
Choosing a Product
Ask your doctor or a dermatologist for advice on which brands of moisturisers work best with acne prone skin. Moisturising acne prone skin at all is risky because even the best moisturisers will clog your pores. First, choose a moisturiser that claims to be noncomedogenic--which means it won't clog your pores. If you try it and after a while you notice a breakout coming on, stop using it, because even though it claims to be noncomedogenic, everyone's skin chemistry is different and it may not work the same for you. You may have to try several different moisturisers before you find one that doesn't cause breakouts.
If your skin is very oily to normal all over your face, you might not need to use moisturiser at all. If your cheeks are very dry, but your T-zone (your forehead and nose area) is very oily or prone to acne, only use the moisturiser on your cheeks.
Apply your moisturiser after you have washed your face and went through your nightly skin care routine to remove all the dirt, oil and make-up that has accumulated on your face throughout the day. Only apply the moisturiser on the areas of your face that are the most dry, and gently smooth a very thin layer on your skin.
If you have skin that is prone to acne breakouts, don't let that keep you from taking care of the spots that need moisturiser to prevent wrinkles, such as the delicate skin around your eyes.