BACKGROUND Obtaining optimal functional outcomes in patients with chronic peripheral nerve injuries (PNIs) remains challenging due to the limited regeneration of the neuromuscular junction (NMJ). Adipose-derived mesenchymal stem cells (AD-MSCs) can differentiate into Schwann-like cells, secrete neurotrophic factors, and recruit native Schwann cells. This study aimed to analyze the effects of AD-MSCs on functional outcomes in a chronic PNI model. METHODS An in vivo study was performed using 20 male Sprague-Dawley rats with chronic PNI of the right sciatic nerve. Rats were divided into two groups: the AD-MSC group (n = 10), receiving human AD-MSC injections in the NMJ; and the control group (n = 10), receiving normal saline injections. Walking track analysis and electrophysiological assessments were performed 8 weeks after the nerve repair. Postmortem gastrocnemius muscle weights and immunohistochemical examinations were also performed. RESULTS The AD-MSCs showed significantly larger fiber diameters than the control group (45.54 [13.1] versus 35.46 [6.64]; p = 0.011). While clinical, electrophysiological, and gastrocnemius muscle weight data suggested a trend toward improved outcomes in the AD-MSCs group, the differences were not statistically significant. CONCLUSIONS AD-MSC implantation may enhance nerve regeneration, as demonstrated by a better outcome profile in the AD-MSCs group. © 2025 Authors.