Introduction: We sought to determine the incidence, risk factors, and prognosis for patients with positive surgical margin (PSM) during partial nephrectomy (PN) for renal cell carcinoma (RCC).Methods: From the Canadian Kidney Cancer information system (CKCis) database, a historical cohort of PN patients with PSM were identified and compared to negative surgical margin (NSM). Risk factors for PSM were examined through multivariable logistic regression. Kaplan-Meier curves were used to compare progression- free survival.Results: Of 1103 patients, 972 (88.1%), 71 (6.4%), and 60 (5.4%) had NSM, PSM, and unknown status, respectively. Median patient age and tumour size were 61 years and 3.0 cm for both groups. From multivariable analysis, pathological stage ≥T3 (odds ratio [OR] 2.51; 95% confidence interval [CI] 1.13–5.60) and Fuhrman grade 4 (OR 5.35; 95% CI 1.11‒25.72) were associated with PSM, whereas age, operative technique, and tumour size were not. Forty-nine (5.0%) patients from the NSM cohort and seven (9.9%) from the PSM cohort had a local/systemic progression of disease (adjusted hazard ratio [HR] 1.4; 95% CI 0.6‒3.6). There were three (0.3%) cancer-related deaths in the NSM group and none in the PSM group. After median followup of 19 (interquartile range [IQR] 5‒42) and 15 (IQR 7–30) months, 855 (91.4%) and 61 (89.7%) patients were alive in the NSM and PSM groups, respectively.Conclusions: PSM occurred in 6.4% of PNs performed for RCC in this pan-Canadian cohort. Higher stage and grade are associated with a higher risk of positive margin. The small association between a PSM and progression suggests that complete nephrectomy is not necessary in patients with a PSM. The main study limitations are lack of nephrometry score and possible reporting bias.