© 2015 European Association of Urology. Background Men aged >65 yr are less likely to receive local therapy for prostate cancer (PCa), perhaps because of concerns about quality-of-life (QOL) outcomes. Objective To describe QOL before and after PCa treatment in men of varying ages. Design, setting, and participants Participants enrolled in CaPSURE who underwent radical prostatectomy, brachytherapy, external beam radiation, androgen deprivation therapy, or active surveillance for localized PCa. Outcome measurements and statistical analysis QOL changes over time were assessed among age groups using repeated-measures mixed models adjusted for race, year, clinical risk, treatment, comorbidities, and an age-time interaction term. Differences are reported as adjusted least-square means and percentage decline. Secondary analyses evaluated age and QOL for local (prostatectomy, radiation) compared to nonlocal treatment (hormonal, surveillance). Results and limitations Older men had lower mean unadjusted pre- and post-treatment QOL scores for nearly all domains. Of the domains evaluated, adjusted mean sexual function, sexual bother, and urinary function showed greater declines from baseline to 2 yr. At 2 yr, more men <60 yr than those >70 yr experienced declines in urinary function (14% vs 9%) and sexual bother (39% vs 17%). Declines in these domains were also greater for local than for nonlocal treatment. Conclusions Definitive treatment for localized disease should not be deferred for older men because of fears regarding QOL declines. Younger men should be counseled about potential post-treatment declines in QOL despite higher absolute QOL scores. Communicating these differences to patients will facilitate more appropriate treatment decision-making in men of all ages. Patient summary In this study we evaluated quality of life before and after treatment for localized prostate cancer in a diverse patient population. Declines in quality of life after treatment varied according to age and treatment. We conclude that counseling about quality of life will help patients of all ages to make more appropriate treatment decisions.