Post-movement beta synchronization (PMBS) modulations have been related to sensory reafferences after movement initiation and inhibitory processes after movement interruption. Although these processes have been separately studied in young and old adults, little is known about the age-related changes in PMBS during selective inhibitory control (i.e. stop a part of an action). The present study examines the age-related modulations of PMBS associated with sensory reafferences and inhibitory processes in selective inhibitory control. Young (n = 17) and old (n = 13) participants performed a switching task first engaging bimanual finger tapping then requiring to stop the left while maintaining the right unimanual tapping (i.e. selective inhibition) at an imperative stimulus. Age groups were compared on behavioral (mean, variability and percentage of errors of inter-tap interval during and after the switching) and electrophysiological (time–frequency and source estimations in the 14–30 Hz beta frequency range) data time-locked on the imperative stimulus. Behaviorally, old adults showed larger variability and percentage of errors during the switching but performed as well as young adults after the switching. Electrophysiologically, PMBS significantly increased after the switching in the old compared to the young group within bilateral frontal and parietal areas. Our results show that the effort to maintain selective inhibition involves increased brain activation in old compared to young adults. The larger PMBS within frontal and parietal regions in old adults may reflect an age-related brain compensation enabling to efficiently maintain post-switching inhibition.