The Automatic Wheelchair Anti-Rollback Device is a supplemental wheel locking device designed for use by individuals with mobility disabilities. As the individual rises from the chair, a pair of brake arms grab the tires to prevent the chair from rolling backwards. Once the user is seated, the device releases and goes into "stand-by" mode and the wheelchair returns to standard operation. Activated by spring tension, a padded lever beneath the wheelchair seat is depressed when the user is seated. This lever is connected to a pair of stainless steel brake arms that are held just off the surface of the rear tires. As the user's weight is lifted from the seat, the spring force causes the lever to rotate and lock the wheels. The greater the rearward force on the chair, the greater the braking power.