The objective is to evaluate the effect of robot-assisted radical prostatectomy (RARP)-related postoperative complications on the 6-month postoperative health-related quality of life (HRQoL). A total of 1008 patients underwent a RARP with or without pelvic lymph node dissection (PLND) between 2012 and 2020 and were invited to complete questionnaires about HRQoL and functional outcomes (urinary incontinence (UI), erectile dysfunction (ED) and urinary complaints (UC)) before and 6 months after RARP. Patient characteristics and postoperative complications up to 90 days after surgery were prospectively recorded. Associations between complications and HRQoL/functional outcomes were assessed by multivariate linear regression analyses. In total, 528 patients (52.4%) were included in the analyses. Complications occurred in 165/528 (31.3%) patients, of which 30/165 (18.2%) had a Clavien–Dindo ≥ III complication. In multivariate regression analyses, postoperative complications were not significantly associated with postoperative HRQoL, UI and ED (p = 0.73, p = 0.72 and p = 0.95, respectively), but were significantly associated with a minor increase in UC (β = 1.7, p < 0.001). More specifically, infectious and urological complications were significantly associated with an increase in UC (β = 1.9, p < 0.001 and β = 0.9, p = 0.004, respectively). The presence of UTI, in particular, was significantly associated with this minor increase (β = 1.5, p = 0.002). Functional outcomes were all significantly associated with the HRQoL at 6 months postoperatively. No significant associations were found between postoperative complications and HRQoL at 6 months after RARP. However, worse functional outcomes were associated with a worse HRQoL at 6 months postoperatively. In addition, postoperative infectious and urological complications were significantly associated with a minor increase in UC.