This paper investigates the stopping power of a weakly coupled magnetized plasma. The effect of the Larmor rotation of the heavy charged test particle is carefully analyzed. The dielectric formalism is employed to obtain a general expression for the stopping power. A quantum mechanical form of the random-phase approximation dielectric function is used so that an arbitrary cutoff procedure is not required. Simple analytical expressions for the stopping power have been found for the cases of high and low projectile velocity of the test particle. The dependence of the stopping power on the angle of incidence is studied. A comparison with numerical solutions is given. It is found that in general a magnetic field reduces the stopping power of the plasma at high velocities, while it increases the stopping power at low velocities.