Single‐particle motion of relativistic electrons in a cusped magnetic field has been studied both analytically and experimentally. The Lagrangian formulation is used to solve for the electron trajectories in some simple magnetic cusp configurations. A threshold energy for transmission through the cusp is found, and confirmed experimentally. Two different electron orbit off‐centering mechanisms are discussed; one arising from a nonzero radial component of particle velocity on the upstream side of the cusp transition, and another arising from the finite width of the cusp transition. Experiments are reported confirming the existence of these off‐centering mechanisms, and the results are compared with theoretical expectations.