Abstract: An adjustable case for a mobile electronic device. The case has a bottom including a main chassis, a fixed holding member fixedly connected with the main chassis, a sliding holding member slidedly connected to the main chassis to slide back and forth, and a tension mechanism biasing the sliding holding member towards the fixed holding member so that the fixed holding member and the sliding holding member squeeze the mobile electronic device when fitted in the case. A plurality of friction members is fixed to a mobile-device-facing surface of the case bottom so that the friction members contact a bottom of the mobile electronic device when the mobile electronic device is fitted in the case. A plurality of raised corner sidewalls is also provided, each sidewall arranged at a corner of the main chassis to extend in a mobile-device-facing direction from the mobile-device-facing surface of the bottom of the case.