In this paper, we present a closed-loop estimation method of permanent magnet synchronous motor parameters by PI controller gain tuning. The idea of the proposed method is to tune the controller to cancel the pole of the motor transfer function with a controller zero and estimate motor parameters from the tuned controller gains. The induced EMF is cancelled by a feedforward compensation term. A systematic tuning procedure is illustrated based on sound theoretical derivations. Compared with the conventional methods using system identification or phasor diagrams, the proposed method does not require complex data analysis or test configuration. Only simple calculation and tuning are sufficient to estimate motor parameters while meeting the desired closed-loop performance. Simulation and experiment are presented to validate the proposed method.