Do neural systems for planning motor actions play a functional role in understanding action language? Across multiple neuroimaging studies, processing action verbs correlates with somatotopic activity in premotor cortex (PMC). Yet, only one neurostimulation study supports a functional role for PMC in action verb understanding: paradoxically, inhibiting PMC made people respond faster to action verbs. Here we investigated effects of PMC excitation and inhibition on action verb understanding using tDCS. Right-handers received excitatory or inhibitory stimulation to left PMC hand areas, then made lexical decisions on unimanual action verbs and abstract verbs. tDCS polarity selectively affected how accurately participants responded to unimanual action verbs. Inhibitory stimulation to left PMC caused a relative increment in performance for right-hand responses, whereas excitatory left PMC stimulation caused a relative decrement. tDCS polarity did not differentially affect responses to abstract verbs. Premotor areas that subserve planning actions also support understanding language about these actions.