Significance Mutations in microtubule motors and their cofactors are associated with several neurological diseases in humans. How disease-associated mutations affect motor function, and consequently have neuropathological effects, is largely unknown. We take advantage of recent advances in the ability to activate transport of the human dynein complex in vitro to functionally characterize 17 disease-associated mutations in the gene encoding its heavy chain. The vast majority of mutations do not affect the ability of dynein to bind a cargo adaptor but do compromise long-range motion of the motor complex. Our findings suggest that defective motility of cargo–motor complexes contributes to dynein-associated neurological phenotypes and highlight several regions of the enigmatic motor that orchestrate its ability to walk over long distances.