An accurate calibration procedure is proposed for a single-feed beam-steerable antenna controlled by varactor-based phase shifters working in differential pairs. The calibration is based on the performance curve of every phase shifter measured from dedicated sampling points on the circuit. A fast selection algorithm based on multi-objective optimization is employed to obtain the control voltages for all differential phase shifter pairs, according to the required phase differences. The final control voltages for a particular beam configuration are validated and fine-tuned on-board at the sampling points. To verify the effectiveness of this procedure, calibrated null-scanning of an 1 × 4 array is demonstrated. The calibrated array can realize null-scanning from -30° to 30° with a null-depth smaller than -21 dB and a null-position tolerance less than 2.5° from 4.75 to 5.25 GHz. These experimentally validated results suggest that the proposed calibration procedure is accurate for beam-scanning arrays fed by varactor-based phase shifters.