A novel magnitude and phase indirect correction technique for active baluns is proposed to solve the amplitude and phase mismatch between outputs at millimeter wave frequency. The input gain and phase errors are equally distributed and recombined by common emitter-common base structure. In the process of distribution and combination, the unknown variable errors between the original external input signals are transformed into the inherent errors caused by the correction circuits. The input gain and phase errors are restricted and indirectly corrected, thus a new ideal differential output signal is produced. The mathematical model and derived formulas confirm the feasibility of the technique in ideal conditions. Furthermore, results from simulations demonstrate the effectiveness of the circuit and validate the theoretical analysis. The simulation results show that the 3-dB bandwidth of the correction circuit is 96-113 GHz and the maximum power gain is 12.7 dB. The differential outputs have gain error less than 0.3 dB and phase error less than 5.3° when the inputs have gain error from 0 dB to 10 dB and phase error from 10° to 110° at 105 GHz. The dc power consumption is 54 mW.