Backgrounds No confirmatory randomized controlled trials (RCTs) have evaluated the efficacy of laparoscopy-assisted distal gastrectomy (LADG) compared with open distal gastrectomy (ODG). We performed an RCT to confirm that LADG is not inferior to ODG in efficacy. Methods We conducted a multi-institutional RCT. Eligibility criteria included histologically proven gastric adenocarcinoma in the middle or lower third of the stomach, clinical stage I tumor. Patients were preoperatively randomized to ODG or LADG. This study is now in the follow-up stage. The primary endpoint is relapse-free survival (RFS) and the primary analysis is planned in 2018. Here, we compared the surgical outcomes of the two groups. This trial was registered at the UMIN Clinical Trials Registry as UMIN000003319. Results Between March 2010 and November 2013, 921 patients (LADG 462, ODG 459) were enrolled from 33 institutions. Operative time was longer in LADG than in ODG (median 278 vs. 194 min, p  < 0.001), while blood loss was smaller (median 38 vs. 115 ml, p  < 0.001). There was no difference in the overall proportion with in-hospital grade 3–4 surgical complications (3.3 %: LADG, 3.7 %: ODG). The proportion of patients with elevated serum AST/ALT was higher in LADG than in ODG (16.4 vs. 5.3 %, p  < 0.001). There was no operation-related death in either arm. Conclusions This trial confirmed that LADG was as safe as ODG in terms of adverse events and short-term clinical outcomes. LADG may be an alternative procedure in clinical IA/IB gastric cancer if the noninferiority of LADG in terms of RFS is confirmed.