Background/Aims: Golimumab (GLM) is an anti-tumor necrosis factor-α drug approved for treating moderate-to-severe active ulcerative colitis (UC). A 52-week post-marketing surveillance (PMS) was initiated to evaluate its safety and effectiveness in patients with UC in Japan. We present an interim report of the ongoing PMS. Methods: Patients received 200 mg of subcutaneous GLM at week 0, 100 mg at week 2, and 100 mg 4 weekly thereafter. The safety analysis set included 392 patients with UC, and the effectiveness analysis set 387 patients. Safety and effectiveness were assessed at week 6. Results: Adverse drug reactions (ADRs) were reported in 8.2% (32/392) and serious ADRs in 4.6% (18/392). The most frequent ADRs were infection and infestation (3.3%), with herpes zoster being the most common. ADRs were significantly higher in patients with concomitant corticosteroid use (odds ratio [OR], 3.45; 95% confidence interval [CI], 1.40–9.68). No significant difference in ADR incidence was observed between patients aged ≥65 and <65 years (OR, 1.23; 95% CI, 0.35–3.47). Six-week effectiveness of GLM was confirmed by a decrease in the partial Mayo score (–2.3; 95% CI, –2.6 to –2.1) and C-reactive protein levels (–0.64; 95% CI, –0.92 to –0.36), including in the biologics-experienced population. Conclusions The safety and effectiveness of GLM at week 6 in a real-world setting were demonstrated in patients with UC in Japan. ADR patterns were consistent with previous reports with no new safety signals. Concomitant corticosteroid use may be associated with increased ADR incidence. The final results of the ongoing PMS are necessary for further evaluation.