We present an exploratory post hoc analysis from the phase 3 CheckMate 214 trial of first-line nivolumab plus ipilimumab (NIVO+IPI) versus sunitinib in a subgroup of 108 patients with advanced renal cell carcinoma (aRCC) without prior nephrectomy and with an evaluable primary tumor, a population under-represented in clinical trials. Patients with clear cell aRCC were randomized to NIVO+IPI every 3 wk for four doses followed by NIVO monotherapy, or sunitinib every day for 4 wk (6-wk cycle). Overall survival (OS), progression-free survival (PFS), objective response rate (ORR), and primary tumor shrinkage were assessed. PFS and ORR were assessed per independent radiology review committee using RECIST version 1.1. With minimum study follow-up of 4 yr for intent-to-treat patients, OS favored NIVO+IPI (n = 53) over sunitinib (n = 55; hazard ratio 0.63, 95% confidence interval 0.40–1.0) among patients without prior nephrectomy. ORR was higher (34% vs 15%; p = 0.0041) and median duration of response was longer with NIVO+IPI versus sunitinib (20.5 vs 14.1 mo); the best overall response was partial response in either arm. A ≥30% reduction in the diameter of intact target renal tumors was achieved in 35% of patients with NIVO+IPI versus 20% with sunitinib. Safety was consistent with the global study population. In conclusion, in patients with aRCC without prior nephrectomy and with an evaluable primary tumor, NIVO+IPI showed survival benefits and renal tumor reduction versus sunitinib. This trial is registered at ClinicalTrials.gov as NCT02231749. Patient summary: In an exploratory analysis of a large global trial (CheckMate 214), we observed positive outcomes (both survival and tumor response to treatment) with nivolumab plus ipilimumab over sunitinib in a subgroup of patients with advanced kidney cancer who did not undergo removal of their primary kidney tumor. This subset of patients represents a population that has not been studied in clinical trials and for whom outcomes with new immunotherapy combination regimens are not yet known. We conclude that treatment with nivolumab plus ipilimumab offers these patients a survival benefit versus sunitinib, consistent with that observed in the overall study, as well as a notable kidney tumor reduction.