Background/Aims: Cold snare polypectomy (CSP) is recommended for colorectal polyps <10 mm; however, the impact of snare size on clinical outcomes remains unclear. This study evaluated the efficacy and safety of 10-mm and 15-mm snares for CSP of small colorectal polyps. Methods: In this prospective multicenter study, patients with 4–10 mm non-pedunculated polyps underwent CSP with either a 10-mm or 15-mm snare. Both snares had identical wire thickness and hexagonal loop design. The primary outcome was histological complete resection rate (CRR). Secondary outcomes included adverse events and technical parameters. Results: In total, 182 patients were enrolled (10-mm group: n = 92; 15-mm group: n = 90). Baseline characteristics, including age, sex, polyp size, morphology, location, and pathology, were comparable between groups. Histological CRRs were 90.2% in the 10-mm group and 91.1% in the 15-mm group (P= 0.483). No significant differences were observed in the presence of submucosal tissue within specimens (P= 0.523), iatrogenic ulcer size (P= 0.532), hematoma occurrence (P= 0.391), or intraprocedural bleeding requiring hemostasis (6.5% vs. 5.6%; P= 0.974). No cases of delayed bleeding or perforation were reported. Logistic regression analysis identified iatrogenic ulcer size > 8 mm as an independent predictor of complete resection (odds ratio, 3.89; 95% confidence interval, 1.15–13.21; P= 0.029); snare size was not significantly associated with CRR (P= 0.519). Conclusions CSP using either a 10-mm or a 15-mm snare for 4–10 mm non-pedunculated colorectal polyps showed no significant difference in complete resection or safety outcomes within this size range. (Clinical Research Information Service [CRIS], KCT0005031)