OBJECTIVE The objectives of this study were to (1) investigate whether electrodiagnostic (EDX) findings reflect the preoperative symptom severity and functional impairment in patients with carpal tunnel syndrome (CTS) and (2) evaluate the relationship between EDX findings and the clinical outcomes reported according to the self-administered patient questionnaires. METHODS Patients diagnosed with idiopathic CTS who underwent carpal tunnel release between May 2016 and July 2018 were included. Carpal tunnel syndrome was clinically diagnosed and confirmed based on the EDX findings. The association between EDX findings, such as motor latency, motor amplitude, sensory latency, sensory amplitude, and severity (mild, moderate, and severe), and the Boston symptom and function scores were analyzed. The change in the Boston symptom and function scores from the preoperative baseline values (visit 1) to those recorded 1 year postoperatively (visit 5) was assessed. The effect of disease severity based on the EDX findings on the change in Boston symptom and function scores by visit was also investigated. RESULTS The EDX severity, motor latency, motor amplitude, sensory latency, and sensory amplitude were not correlated with the Boston symptom and function scores preoperatively and postoperatively. Electrodiagnostic severity did not affect the improvement in the Boston symptom and function scores recorded at each visit. CONCLUSIONS We found no association between the EDX severity and perioperative Boston questionnaire scores, and the degree of improvement in patient symptoms and function did not differ according to the CTS severity based on the EDX findings. METHODS Level IV, Prognostic study.