PurposeTo compare the outcomes of robotic partial nephrectomy (RPN) with those of open PN (OPN) in patients with highly complex renal tumors defined as RENAL nephrometry score ≥ 10Materials and methodsWe analyzed clinical data from a total of 149 patients who underwent OPN or RPN for a highly complex renal mass at our institution between 2003 and 2017. Perioperative data, complication profiles, functional outcomes, pathologic variables, and oncologic outcomes were evaluated in both groups.ResultsThe median (interquartile range, IQR) patient age was 52.0 (42.0–59.0) years, and the median (IQR) follow-up period was 30.0 (7.0–54.0) months. Among the patients, 64 (43.0%) and 85 (57.0%) underwent OPN and RPN, respectively. The RPN group showed higher rates of clinical T1b and ≥ T2 than the OPN group (p = 0.019). There were no significant differences between the groups in terms of intraoperative outcomes such as operation time, estimated blood loss, warm ischemic time, and transfusion. Notably, the RPN group showed significantly shorter length of hospital stay than the OPN group (p < 0.001). Regarding the complication profiles and renal functional outcomes, no significant differences were reported between the groups. The estimated glomerular filtration rate decline from baseline at the last follow-up showed no significant differences between the two groups (p = 0.351). Kaplan-Meier survival analysis also showed no significant differences in survival outcomes between the groups (log-rank test, all p > 0.05).ConclusionsRPN performed in patients with highly complex renal tumors offers perioperative, functional, and oncologic outcomes comparable to those associated with OPN.