The risk factors for immediate post-polypectomy bleeding (IPPB) after cold snare polypectomy (CSP) are not well-known. We sought to define such risk factors and develop a predictive risk-scoring model. This prospective observational study included 161 polyps (4–9 mm in diameter) that were removed via CSP from 118 patients during the period from June to September 2019 in 2 tertiary hospitals. IPPB was defined as post-polypectomy bleeding within 24 hours or grade 3 or 4 intraprocedural bleeding requiring endoscopic hemostasis. IPPB incidences according to grade were 13.0% (21/161) (grade 3) and 0% (grade 4). Univariate analysis showed that the polyp size and morphology, as well as iatrogenic ulcer size and shape, were significantly associated with IPPB. Multivariate analysis showed that polyp size [6–9 mm vs 4–5 mm, odds ratio (OR) 3.72, 95% confidence interval (CI) 1.28–10.79], polyp morphology (polypoid vs non-polypoid, OR: 3.93, 95% CI: 1.22–12.64), and iatrogenic ulcer size (≥10 vs ≤ 9 mm, OR: 3.12, 95% CI: 1.04–9.38) were significantly associated with IPPB. We created a four-marker risk-scoring model to predict IPPB after CSP; we summed the points assigned for the 4 factors. At a cutoff of 2, the sensitivity was 85.7% and the specificity was 65.0%; at a cutoff of 3, the sensitivity was 65% and the specificity was 90.0%. Polyp size and morphology, as well as iatrogenic ulcer size and shape, were associated with IPPB after CSP. The four-marker risk-scoring model appears to effectively predict IPPB after CSP (Clinical Research Information Service: KCT0004375).