An extension ladder stabilizer includes a ladder rung engagement rod having threads along at least a portion of its length and configured to be disposed in and project from each end of a hollow tubular rung of an extension ladder, a pair of internal supports having a substantially gear shaped hole in each, a pair of external supports having a substantially gear shaped boss with a through hole on a first face and an anchor channel on a second face opposite the first face on each, and a pair of ground engagement members. In a ladder stabilizing configuration, the extension ladder stabilizer is installed on a ladder and the ground engagement members are passed through the anchor channels and into the ground to secure the ladder from side slipping, kicking back, and kicking over when in use.