A shopping cart locking system. A locking assembly includes a generally cylindrical retainer having a vertically extending axial slot along the first edge. A rigid bracket is secured along a second edge of the retainer. A clevis at the lower extent of the bracket has apertures, a first vertical space, an upper member with two forwardly extending fingers defining a second vertical space vertically aligned with the first space of the clevis. A foot is selectively positionable between an upper inactive orientation and a lower orientation into frictional braking contact with a wheel below the foot. An upper end of the foot has a generally rectangular recess. A coupling pin extends horizontally through a central extent of the foot and through the recess. A joining leg has an upper end with an aperture located between the first space of the clevis. A first pin rotatably couples the leg to the clevis. The leg has a lower end extending into the recess of the foot. A coupling pin pivotably couples the leg and the foot through an aperture in the leg and an aperture in the foot.