Background/aim: We performed this prospective randomized double-blind study to compare the effects of nefopam versus ketorolac in intravenous fentanyl-based patient-controlled analgesia (PCA) after shoulder arthroscopic orthopedic surgery. Materials and methods: Ninety-two patients were randomly divided into two groups to receive intravenous PCA. Patients were assigned to either the nefopam group (nefopam 120 mg and fentanyl 20 µg/kg) or the ketorolac group (ketorolac 2 mg/kg and fentanyl 20 µg/kg). Pain was assessed on a visual analogue scale (VAS) and a numeric rating scale (NRS). Additionally, patient satisfaction, adverse events, and vital signs were monitored. Results: There were no significant differences in VAS score (P = 0.48) or NRS score (P = 0.15) between the two groups. Similarly, patient satisfaction did not differ between the two groups [8.5(0.8) vs. 8.2(1.0), P = 0.14]. There were no statistically significant differences in the incidence of nausea (P = 0.72), vomiting (P = 0.46), urinary retention (P = 0.82), sweating (P = 0.49), or dizziness (P = 0.45) between the two groups. Likewise, there were no differences in heart rate [78.2(7.7) vs. 75.2(6.5), P = 0.18] or SpO2 [98.4(1.8) vs. 98.5(1.9), P = 0.83]. Conclusion: Nefopam is an appropriate alternative for co-administration with fentanyl-based PCA in patients who have difficulty using nonsteroidal antiinflammatory drugs.