Purpose Robotic assisted radical prostatectomy has largely replaced open radical prostatectomy for the surgical management of prostate cancer despite conflicting evidence of superiority with respect to disease control or functional sequelae. Using population cohort data, in this study we examined sexual and urinary function in men undergoing open radical prostatectomy vs those undergoing robotic assisted radical prostatectomy. Materials and Methods Subjects surgically treated for prostate cancer were selected from 2 large population based prospective cohort studies, the Prostate Cancer Outcomes Study (enrolled 1994 to 1995) and the Comparative Effectiveness Analysis of Surgery and Radiation (enrolled 2011 to 2012). Subjects completed baseline, 6-month and 12-month standardized patient reported outcome measures. Main outcomes were between-group differences in functional outcome scores at 6 and 12 months using linear regression, and adjusting for baseline function, sociodemographic and clinical characteristics. Sensitivity analyses were used to evaluate outcomes between patients undergoing open radical prostatectomy and robotic assisted radical prostatectomy within and across CEASAR and PCOS. Results The combined cohort consisted of 2,438 men, 1,505 of whom underwent open radical prostatectomy and 933 of whom underwent robotic assisted radical prostatectomy. Men treated with robotic assisted radical prostatectomy reported better urinary function at 6 months (mean difference 3.77 points, 95% CI 1.09-6.44) but not at 12 months (1.19, -1.32-3.71). Subjects treated with robotic assisted radical prostatectomy also reported superior sexual function at 6 months (8.31, 6.02-10.56) and at 12 months (7.64, 5.25-10.03). Sensitivity analyses largely supported the sexual function findings with inconsistent support for urinary function results. Conclusions This population based study reveals that men undergoing robotic assisted radical prostatectomy likely experience less decline in early urinary continence and sexual function than those undergoing open radical prostatectomy. The clinical meaning of these differences is uncertain and longer followup will be required to establish whether these benefits are durable.