We have used the variational procedure in the effective-mass and nondegenerate parabolic band approximations in order to investigate the effects of a magnetic field on the exciton effective mass and dispersion in semiconductor heterostructures. Calculations are performed for bulk GaAs, and two-dimensional and quasi-two-dimensional excitons in coupled $\mathrm{Ga}\mathrm{As}\penalty1000-\hskip0pt(\mathrm{Ga},\mathrm{Al})\mathrm{As}$ quantum wells for applied magnetic fields perpendicular to the layers. A simple hydrogenlike envelope wave function provides the expected behavior for the exciton dispersion in a wide range of the center-of-mass momenta, and an analytical expression for the exciton effective mass is obtained. Present results lead to a magnetic-field dependent exciton effective mass and dispersion in quite good agreement with available experimental measurements in coupled $\mathrm{Ga}\mathrm{As}\penalty1000-\hskip0pt(\mathrm{Ga},\mathrm{Al})\mathrm{As}$ quantum wells.