The force variation on a particle during a bubble-particle collision is investigated in two different liquid phases: (1) distilled water and (2) 80 wt% glycerin in water solution. The force variations on a stationary particle due to the collision are experimentally measured and the collision processes are visualized. A simple analytical model of the collision process is developed to account for the pressure force on a particle induced by bubble-particle contact. To obtain physical insight into the bubble-particle collision process, numerical simulations are performed. The computational study agrees closely with the experimental results. Furthermore, the collision;between a falling particle and a rising bubble is simulated and compared to the stationary particle case. The simulation of the collision between a bubble and a stationary particle reveals that the force on the particle oscillates: first increases, then decreases, and again increases. The magnitude of the force variation is comparable to the product of the hydrostatic pressure difference across the bubble height and the cross-sectional area of the particle. When the collision takes place in water, the pressure force predominates and the particle experiences both upward and downward forces. When the collision takes place in the glycerin solution, both pressure and viscous forces predominate and the force on the particle induced by the rising bubble is always upward. If a particle is moving downward with a speed relatively faster than that of the rising bubble, the particle experiences an upward drag force due to its downward motion before colliding with a bubble. At the beginning of the collision, the upward force decreases greatly, and recovers quickly. At the end of the collision process, the upward force increases significantly due to the pressure and the wake effect of the bubble. The magnitude of the force variation is comparable to the drag force on the particle before the collision.