With the current patterns of adoption and use of robotic surgery and improvement in the overall survival of patients with prostate cancer, it is important to evaluate the immediate and long-term cost implications of treatments for patients with prostate cancer. To compare health care costs and use 1 year after open radical prostatectomy (ORP) vs robotic-assisted radical prostatectomy (RARP). This retrospective cohort study used a US commercial claims database from January 1, 2013, to December 31, 2018. A total of 11 457 men aged 18 to 64 years who underwent inpatient radical prostatectomy for prostate cancer and were continuously enrolled with medical and prescription drug coverage from 180 days before to 365 days after inpatient prostatectomy were identified. An inverse probability of treatment weighting analysis was performed to examine the differences in costs and use of health care services by surgical modality. Data analysis was conducted from September 2019 to July 2020. Type of surgical procedure: ORP vs RARP. Three outcomes within 1 year after the inpatient prostatectomy were investigated: (1) total health care costs, including reimbursement paid by insurers and out of pocket by patients; (2) health care use, including inpatient readmission, emergency department, hospital outpatient, and office visits; and (3) estimated days missed from work due to health care use. Of the 11 457 patients who underwent inpatient prostatectomy, 1604 (14.0%) had ORP and 9853 (86.0%) had RARP and most patients (8467 [73.9%]) were aged 55 to 64 years. Compared with patients who underwent ORP, those who received RARP had a higher cost at the index hospitalization (mean difference, $2367; 95% CI, $1821-$2914; P < .001), but similar total cumulative costs were observed within 180 days (mean difference, $397; 95% CI, -$582 to $1375; P = .43) and 1 year after discharge (-$383; 95% CI, -$1802 to $1037; P = .60). One-year postdischarge health care use was significantly lower in the RARP compared with ORP group for mean numbers of emergency department visits (-0.09 visits; 95% CI, -0.11 to -0.07 visits; P < .001) and hospital outpatient visits (-1.5 visits; -1.63 to -1.36 visits; P < .001). The reduction in use of health care services among patients who underwent RARP translated into additional savings of $2929 (95% CI, $1600-$4257; P < .001) and approximately 1.69 fewer days (95% CI, 1.49-1.89 days; P < .001) missed from work for health care visits. Total cumulative cost in this study was similar between ORP and RARP 1 year post discharge; this finding suggests that lower postdischarge health care use after RARP may offset the higher costs during the index hospitalization.