Since a fiber suspension is opaque and fibers are prone to flocculate, it is difficult to measure the bubble rise velocity in a fiber suspension. In this study, a low-cost method combining an imaging technique with a conductivity technique is developed to estimate the rise velocity of single bubbles in a fiber suspension. The bubble velocity in a bleached kraft hardwood fiber suspension is investigated at the mass concentration of 0.2-1.0% (oven dry) and at the superficial velocity of 0.01 to 0.04 m/s. Finally, an empirical correlation among the bubble drag coefficient, Reynolds number (based on bubble size and water viscosity), and crowding number is developed for the fiber suspension.