Background: Peripheral nerve injury can happen for a variety of causes. Despite major breakthroughs in microsurgery, nerve repair results are not always sufficient. Methods: Thirty-two Wistar albino rats were split into four groups: primary nerve repair (PNR), PNR with vitamin D3 treatment, nerve crush injury (NCI), and NCI with vitamin D3 treatment. In the PNR + D3 and NCI + D3 groups, 1 mcg/kg of vitamin D3 was given intraperitoneally on days 1, 3, 5, and 7 of the 12-week healing period. Electrophysiological measurements were taken prior to the injury. At 12 weeks after damage, a hot plate test was performed to assess acute pain, and the electrophysiological measurements were repeated. Before the rats were sacrificed, biopsy samples from the right sciatic nerve were collected for histopathological evaluation. Results: Post-healing action potential values were not statistically different between the PNR and PNR + D3 groups; however, they were considerably lower in the NCI + D3 group than in the NCI group. The reaction time in the hot plate test was considerably slower in the D3-treated groups compared to the control groups. Histopathology score was substantially higher in the PNR + D3 group as compared to the PNR group, and lower in the NCI + D3 group as compared to the NCI group. Conclusions: Other than improved myelination, vitamin D3 treatment following primary repair of transected nerves produced no statistically significant improvement. Vitamin D3 treatment caused a negative impact on the crush injury, as assessed by the findings of histopathology and electrophysiological measurements. Overall, the results indicate that the efficacy of vitamin D3 treatment may vary depending on the type of injury.