Exposure to communicative gestures, through their parents' use of gestures, is associated with infants' language development. However, the mechanisms supporting this link are not fully understood. In adults, sensorimotor brain activity occurs while processing communicative stimuli, including both spoken language and gestures. Using electroencephalogram (EEG) mu rhythm desynchronization (mu ERD), a marker of sensorimotor activity, we examined whether experimental manipulation of infants' exposure to gestures would affect language development, and specifically whether such an effect would be mediated by changes in sensorimotor brain activity. Mu ERD was measured in 10- to 12-month-old infants (N = 81; 42 male; 15% Hispanic, 62% White) recruited from counties surrounding a large mid-Atlantic university while they observed an experimenter gesturing toward or grasping an object. Half of the infants were randomized to receive increased gesture exposure through a parent-directed training. All 81 infants provided behavioral (infant and parent pointing and infant vocabulary) data prior to intervention and 72 provided behavioral data postintervention. Forty-two infants provided usable (post artifact removal) EEG data prior to intervention and 40 infants provided usable EEG data post-intervention. Twenty-nine infants provided usable EEG data at both sessions. Increased parent gesture due to the intervention was associated with increased infant right lateralized mu ERD at follow-up, but only while observing the experimenter gesturing not grasping. Increased mu ERD, again only while observing the experimenter gesture, was associated with increased infant receptive vocabulary. This is the first evidence suggesting that increasing exposure to gestures may impact infants' language development through an effect on sensorimotor brain activity.