We sought to examine the impact of baseline patient characteristics and perioperative outcomes on postoperative hospital length of stay (LOS), following the robot-assisted radical prostatectomy (RARP). We retrospectively reviewed consecutive patients receiving RARP at our institution by two surgeons between January 2012 and March 2014 (n = 274). Baseline patient characteristics were collected, including Charlson comorbidity index (CCI). Discharge criteria were identical for all patients and included: return of bowel function, pain controlled with oral medications, and ambulation without assistance. LOS was calculated as the number of midnights spent in the hospital following surgery. Postoperative hospital LOS was equal to 1 day for 225 patients and >1 day for 49 patients. Baseline patient and tumor characteristics, including age, race, body-mass index (BMI), pathologic stage, and Gleason score, were not significantly different. Mean operative time was shorter for patients with LOS > 1 day (155 vs. 173 min, p < 0.01) on univariate analysis. Patients with LOS > 1 day were more likely to have had a complication: 8/49 (17 %) vs. 14/225 (6 %), p < 0.01. However, multivariate logistic regression found baseline CCI > 2 as the only independent predictor of LOS > 1 day (OR = 3.2, p = 0.03), controlling for age, race, BMI, Gleason score, tumor stage, blood loss, operative time, and occurrence of complication. In our experience, baseline patient comorbidity, quantified by CCI, was the only independent predictor of hospital LOS greater than 1 day following RARP. Preoperative assessment of patient comorbidity should be used to better counsel patients on their anticipated postoperative course.