This brief proposes an auto-tuning proportional-type synchronization controller for dc motor speed applications with consideration of parameter and load variations. The proposed algorithm is comprised of two parts: a proportional-type speed tracking controller with a disturbance observer (DOB) and second a synchronizer driven by an auto-tuning algorithm. The first feature is to propose an auto-tuning synchronizer to reduce synchronization error during transient operations. The second is to introduce a DOB so that the proportional-type controller guarantees tracking and synchronization performance recovery without offset error. Experimental data is provided to convincingly show the effectiveness of the suggested scheme using a 50-W dual dc motor drive system.