Objective The aim of this study was to review regret following treatment for localized prostate cancer, including factors associated with higher levels of regret, regret after specific treatments and the use of interventions to modify the likelihood of regret. Methods Online databases including Medline, CINAHL, EMBASE, EBSCO and PsycINFO were searched in June 2014, using the terms 'prostate' and 'regret' for publications written in English and appearing in print since the year 1997. Results Of 422 articles identified by the search criteria, 28 contained analyzable data regarding 8118 patients. The most commonly identified factors associated with regret after prostate cancer treatment were treatment toxicity factors, especially sexual and urinary function. Other factors included older age and longer time since treatment. The levels of regret were generally higher after radical prostatectomy than external beam radiotherapy or brachytherapy. Decision-making aids were the most commonly used method for reducing the likelihood of regret and were effective. Conclusions This is the first systematic review of regret following treatment for localized prostate cancer. Suggestions for the future study of regret in this setting can be made. These include the use of a standardized scale; recognizing levels of regret as low, medium or high; and separately identifying the decision made when patients have combinations of treatments such as surgery followed by radiotherapy.