The impact of salvage radiotherapy (SRT) and its timing on health-related quality of life (HRQoL) in prostate cancer patients is still unclear.To compare the HRQoL of patients who underwent SRT with that of patients who underwent radical prostatectomy (RP) only and to investigate whether SRT timing is associated with HRQoL.All SRT patients (n=241) and all RP-only patients (n=1005) were selected from a prospective database (2004-2015). The database contained HRQoL and prostate problem assessments up to 2 yr after last treatment.Mixed effects growth modelling adjusting for significant differences in patient characteristics and baseline HRQoL was used to analyze the association between: (1) "treatment" (RP-only vs SRT) and (2) "timing of SRT" with changes in HRQoL.SRT patients showed significantly (p<0.05) poorer recovery from urinary, bowel, and erectile function after their last treatment (clinically meaningful difference for urinary and erectile function). Patients with a longer interval (≥ 7 mo) between RP and SRT reported significantly better sexual satisfaction after SRT (p=0.02), and a better urinary function recovery (p=0.03). Limitations of the study include the nonrandom design and the variability in timing of HRQoL measurements.Up to 2 yr after treatment, SRT patients reported poorer HRQoL in several HRQoL domains compared with RP-only patients, but not in overall HRQoL. Delaying the start of SRT after RP may limit the incidence and duration of urinary and sexual problems. Nevertheless, decisions regarding SRT timing should also be based on the potential benefits in disease recurrence.Patients who receive radiotherapy after surgery may experience poorer urinary, bowel, and erectile function compared with patients who undergo surgery only. Although more research is needed, delaying radiotherapy seems to limit its impact on urinary and sexual functioning.