Find 7 one-bedroom apartments for rent in Mountainside, NJ on ForRent.com. Compared to a studio, a one-bedroom apartment offers a separate and defined bedroom, bathroom, and living area with a full kitchen. These apartments give you privacy and a quiet retreat from the main living area, as well as a common space to host guests. One-bedroom rentals are great for individuals, couples, or other renters in need of minimal space with essential amenities.