Brushed DC motors are widely used in industrial applications where speed regulation requirements are critical. Speed control of DC motor using incremental optical encoder feedback mechanism and Simulink model of DC Motor is presented in this paper. Quadrature decoding of encoder pulses is done to measure motor speed at a sampling instant and PID controller algorithm is applied to compute control variable in the form of PWM. Motor driver, here the H-bridge circuit, responds to the PWM signal and produces voltage proportional to PWM duty cycle that actuates DC motor resulting in motor speed proportional to PWM duty cycle. Experiments show that proper tuning of PID parameters result in smooth tracking of the reference speed.