Catheter-related bladder discomfort (CRBD) is a distressing symptom complex after surgery, especially in male patients who have had urinary catheterization under general anesthesia. In this prospective, randomized, controlled trial, we compared dorsal penile nerve block (DPNB) with 0.33% ropivacaine with intravenous tramadol 1.5 mg kg−1 in prevention of CRBD, as well as the incidences of postoperative side effects. Fifty-eight male patients aged 18 to 50 years, undergoing elective liver surgery and limb surgery with urinary catheterization, were enrolled and divided randomly into 2 groups. In the DPNB group, patients were given dorsal penile nerve block with 15 mL of 0.33% ropivacaine, and in the tramadol intravenous administration (TRAM) group, patients were given 1.5 mg kg−1 tramadol after the completion of surgery before extubation. The primary outcome was the incidence of CRBD, and the secondary outcomes included the severity of CRBD, postoperative side effects, postoperative pain, and the acceptance of urinary catheterization. Patients were evaluated upon arrival to postanesthetic care unit (PACU), at 0.5, 1, 2, 4, and 6 hours after patients’ arrival in the PACU for outcomes. The incidence of CRBD was significantly lower in the DPNB group than in the TRAM group, either upon arrival to PACU (10.3% vs 37.9%, P = 0.015), or at 0.5 hours (3.4% vs 34.5%, P = 0.003), 1 hours (3.4% vs 37.9%, P = 0.001), 2 hours (6.9% vs 34.5%, P = 0.010), and 4 hours (6.9% vs 27.6%, P = 0.039) after patients’ arrival in PACU. Compared with the TRAM group, the severity of postoperative CRBD upon arrival to PACU (P = 0.011) and at 0.5 hours (P = 0.005), 1 hours (P = 0.002), 2 hours (P = 0.005), 4 hours (P = 0.017), and 6 hours (P = 0.047) after patients’ arrival in PACU were all significantly reduced in the DPNB group. The incidences of postoperative nausea, vomiting, dizziness, and sedation were decreased significantly in the DPNB group compared with the TRAM group (P