Objectives: Translingual neurostimulation (TLNS) studies indicate improved outcomes in neurodegenerative disease or spinal cord injury patients. This study was designed to assess the safety and efficacy of TLNS plus targeted physical therapy (PT) in people with a chronic balance deficit after mild-to-moderate traumatic brain injury (mmTBI).Materials and Methods: This international, multicenter, randomized study enrolled 122 participants with a chronic balance deficit who had undergone PT following an mmTBI and had plateaued in recovery. Randomized participants received PT plus either high-frequency pulse (HFP; n = 59) or low-frequency pulse (LFP; n = 63) TLNS. The primary efficacy and safety endpoints were the proportion of sensory organization test (SOT) responders (SOT composite score improvement of ≥15 points) and fall frequency after five weeks of treatment, respectively.Results: The proportion of SOT responders was significant in the HFP + PT (71.2%) and LFP + PT (63.5%) groups compared with baseline (p < 0.0005). For the pooled population, the SOT responder rate was 67.2% (p < 0.00005), and there were clinically and statistically significant improvements in SOT composite scores after two and five weeks (p < 0.0005). Both groups had reductions in falls and headache disability index scores. Mean dynamic gait index scores in both groups also significantly increased from baseline at weeks 2 and 5.Conclusions: Significant improvements in balance and gait, in addition to headaches, sleep quality, and fall frequency, were observed with TLNS plus targeted PT; in participants who had a chronic balance deficit following an mmTBI and had plateaued on prior conventional physiotherapy.