The application of vibration to a muscle is known to activate its muscle spindle receptors; the same receptors that are activated when the muscle is lengthened. Both muscle length and vibration are known to affect corticospinal excitability. However, their combined effects on corticospinal excitability have not been established. Thus, single pulse transcranial magnetic stimulation was applied before and after first dorsal interosseous muscle vibration at four different muscle lengths. Post-vibration motor evoked potentials were significantly higher and tonic vibration reflexes were elicited at the longest muscle length condition. As both muscle length and vibration are known to increase muscle spindle activation, the current results suggest increased corticospinal excitability when these conditions are combined may be due to increased spindle activity. More research is needed to further understand the mechanisms within the corticospinal pathway.