An infant seat mounted on a shopping cart permits an infant to be carried while avoiding interference with a nesting function of the shopping cart. The infant seat includes a mounting plate that can be fastened to the shopping cart at a gate that can pivot about an axis to permit the infant seat to pivot with the gate during shopping cart nesting. The infant seat can be mounted to the shopping cart at a desired mounting angle with the optional use of wedges that have particular angles of inclination. The combination of wedges can be used to produce a desired mounting angle for different types of shopping carts to which the infant seat is fastened. Mounting angle indicia can be provided on the infant seat to help determine a proper or desired mounting angle for the infant seat. A gauge to determine a proper or desired mounting angle can be used with the indicia to obtain the desired mounting angle. The infant seat is weather resistant and provides a robust support for temporarily transporting an infant on a shopping cart.