Find 51 apartments for rent in Diamond Bar, CA with an in-unit washer and dryer. When a rental has in-unit laundry, the washer and dryer are included with the apartment instead of in a communal room. All your laundry needs can be taken care of from the comfort of your own home. Apartments with in-unit washers and dryers are usually a bit more expensive than apartments without them. That said, the convenience and time savings of having an in-unit laundry is often worth the extra cost.