Neuromodulation of the primary motor cortex (M1) in pair with physical therapy may be a promising method for improving motor outcomes after spinal cord injury (SCI). Increased excitability of the corticospinal motor pathways (i.e. corticomotor excitability) has shown to be associated with improved motor learning and skill acquisition. Intermittent theta burst stimulation (iTBS) is a form of non-invasive brain stimulation which can increase corticomotor excitability, as measured by an increase in the amplitude of motor evoked potentials (MEPs). Our long-term goal is to determine if iTBS paired with physical therapy can improve motor re-education of upper limb muscles after tendon or nerve transfer in individuals with tetraplegia. Proximal upper limb muscles, such as the biceps brachii, can be surgically transferred to restore elbow extension. However, the ability for iTBS to increase the corticomotor excitability of proximal muscles such as the biceps, and muscles affected by spinal cord injury is currently unclear. The majority of studies involving iTBS have targeted the first dorsal interosseous (FDI) in non-impaired individuals. While these studies have found iTBS to increase the amplitude of MEPs, the effects often vary across participants resulting in negative findings group wide. One study which targeted the flexor carpi radialis (FCR), a muscle more proximal than the FDI, found that differences in the resting motor thresholds (RMT) between the FCR and its antagonist muscle (extensor carpi radialis) appeared to determine the efficacy of iTBS. However, these observed effects may not translate to the biceps due to differences in corticospinal control across muscles. Therefore, the purpose of the present studies was to determine the effect of iTBS on the corticomotor excitability of the biceps, as measured by MEP amplitudes, in non-impaired individuals and individuals with tetraplegia. Participants completed three sessions of the protocol, each including sham and active iTBS. Sessions were separated by a minimum of three days to prevent the potential for carry over effects. Participants were instrumented with surface electromyography electrodes on the biceps and its primary antagonist of their dominant arm. The maximal compound action potential (Mmax) was recorded from these muscles for the normalization of MEPs (nMEP). Resting motor threshold (RMT) and active motor threshold (AMT) were then determined by delivering single pulse TMS. MEPs were recorded via single pulse TMS delivered at an intensity of 120% RMT, at intervals before, 10, 20, and 30 min after sham and active iTBS. The iTBS parameters consisted of three pulses presented at 50 Hz, repeated every 200 ms for 2 s at an intensity of 80% of the participant’s AMT. Two second bursts were repeated every 8 s for a total of 600 pulses. Single pulse TMS and iTBS were both delivered with a Super Rapid Plus stimulator via a 70 mm figure-of-eight coil (Magstim). No change in nMEP amplitude after either sham or active iTBS was found in the non-impaired group. However, the SCI group showed an increase in nMEP amplitude after active iTBS relative to sham, suggesting an increase in corticomotor excitability. Furthermore, there was no correlation in either group between the changes in nMEP amplitudes and the difference between the RMT of the biceps and its antagonist (triceps brachii). While further research is needed before combinatorial therapies can be achieved, this study suggests that iTBS may be a promising method for improving motor function in those with tetraplegia.