The velocity matching rule of a flocking system (also known as alignment) ensures that boids attempt to match the velocities of their neighbours. Each flock member will continually compare its own velocity with that of its immediate neighbours and make adjustments to its own velocity based on the average of all neighbours. Because all flock members will perform this same operation, the overall effect is that the flock remains well aligned.

Velocity Matching is complementary to the separation rule as it stands to reason that if a boid does a good job of matching velocity with its neighbours, it is unlikely to collide with them.