Background: Comorbidity increases the risk of general complications for patients undergoing kidney surgery. Less is known about the effect of comorbidity on urologic complications after surgery, especially for patients with renal cell carcinoma (RCC). Access to care may impact comorbidity and surgical management among patients with RCC. We aimed to assess the effect of comorbidity on postoperative complications and readmissions among patients with RCC in the Military Health System, which provides universal access to care to eligible beneficiaries. Methods: We identified a cohort of patients aged 18 and older diagnosed with American Joint Committee on Cancer stage I-III RCC between 2001 and 2014 who received either partial or total nephrectomy in the MilCanEpi database. Outcomes included 90-day general cardiac, respiratory, vascular and surgical complications, urologic complications of surgical site infection, seroma, urinoma, acute renal failure, urinary tract infection, urinary incontinence, dysuria, or kidney stones; and hospital readmissions. The association between Elixhauser comorbidity (0, 1-2, 3-4, 5 or more) and outcomes were estimated using multivariable Poisson regression and expressed as adjusted rate ratios (ARRs) with 95% confidence intervals (CIs). Results: The study included 1,470 patients with a median (IQR) comorbidity count of 2 (0-3) conditions. Overall, patients with 5 or more comorbidities had elevated rates of general complications (ARR=1.47, 95% CI=0.96, 2.23) relative to patients with no comorbidity. For urologic complications, patients with 3-4 comorbidities (ARR=1.68, 95% CI= 1.22, 2.31) and 5 or more comorbidities (ARR=1.95, 95% CI=1.39, 2.72) had statistically significant higher risks relative to patients with no comorbidity. Patients with 5 or more comorbidities also had a higher risk of readmission (ARR=1.68, 95% CI=1.06, 2.67 vs. no comorbidity) while the risks were not statistically different for patients with lower comorbidity. Conclusions: The results of our study demonstrate the increased risk for postoperative urologic complications and readmissions for patients with RCC and high comorbidity burden in a universal healthcare system. This highlights the importance of comorbidity management in pre- and postoperative surgical care among patients with RCC.