Purpose To investigate the presence of regret in patients about having followed an active surveillance (AS) protocol. The secondary aim was to identify variables that influence regret. Methods From February 2006 to May 2014, 204 patients discontinued the AS protocols and were invited to enter the study. Sociodemographic variables were collected at AS enrollment, together with health-related quality of life (Functional Assessment of Cancer Therapy-Prostate version [FACT-P]) and coping (Mini-Mental Adjustment to Cancer). Patients were asked to complete a Treatment Regret Scale as well as the FACT-P questionnaire. Clinical data were gathered, as well as time of stay within the AS protocol, reason for discontinuing AS, kind of post-AS treatment, and time elapsed since AS discontinuation. Questionnaires were completed by 105 patients (51.5% of those who had been invited to enter the study). Results Most of the patients had a low or null degree of regret on the Treatment Regret Scale from 0 to 100 (82/105 patients [78.1%] obtained a score <30, and about 30% of the sample had a score equal to zero). Only 5 patients (4.7%) scored 60 or more, indicating some degree of regret. None of the statistical tests between regret scores and a number of analyzed variables reached significance. Conclusions These results show that the degree of regret about following an AS protocol and after its discontinuation because of entering active treatment was very low. The regret after AS was not related to sociodemographic or clinical factors.