The aim of the present study was to determine whether oncologic outcomes and adverse events associated with active on/off intermittent antiandrogen monotherapy (daily bicalutamide, 50 mg per day) are comparable with those of standard external beam radiation therapy (EBRT) or combined androgen blockade (CAB) therapy in prostate cancers with positive surgical margins after radical prostatectomy. Two hundred twenty-three patients with positive surgical margins post-radical prostatectomy who underwent active surveillance (AS, n = 32), EBRT without hormone therapy (n = 55), intermittent antiandrogen monotherapy without EBRT (IAAM, n = 50), or CAB without EBRT (n = 86), between 2007 and 2014, were reviewed retrospectively. Pathologic outcomes, biochemical recurrence rates, radiological disease progression, and adverse events were collected from medical records. Biochemical recurrence rates, biochemical recurrence-free survival rates, and radiological recurrence were not different between the groups (P = 0.225, 0.896, and 0.284, respectively). Adverse event rates and severities were lower for IAAM compared with EBRT or CAB (both P < 0.05), but were comparable to those for AS (P = 0.591 and 0.990, respectively). Grade ≥3 adverse events were not reported in the IAAM or AS groups. Erectile dysfunction and loss of libido rates were lower in the IAAM group compared with the EBRT and CAB groups (P = 0.032). Gastrointestinal complications were more frequently reported in the EBRT group (P = 0.008). Active on/off IAAM treatment might be an appropriate treatment option for patients with positive surgical margins after radical prostatectomy. Furthermore, regarding oncologic outcomes, IAAM was comparable to standard EBRT but had a milder adverse event profile.