Problematic use of prescribed and over-the-counter analgesics is widespread and increasing among people with chronic pain, but the availability of preventative and treatment services is limited. We evaluated a 21-day online intervention based on compassionate mind training in a prospective, randomized-controlled trial. The participants were 73 adults with concerns about their use of analgesics for chronic pain conditions. Participants completed measures of analgesic use, misuse and dependence, plus self-criticism and self-reassurance (self-inadequacy, self-reassurance, and self-hate), cognitive impulsivity (negative urgency, lack of perseverance, lack of premeditation, sensation-seeking, and positive urgency) and behavioral impulsivity (delay discounting) at baseline, postintervention, and 1-week postintervention follow-up. Following baseline assessment, participants were randomized to compassionate mind training (CMT; n = 38) or relaxation music (n = 35), both delivered online. No adverse events or safety issues were reported and high participant retention and exercise completion rates showed that the intervention was acceptable to participants. Repeated measures analysis of variance showed that by comparison with relaxation music, the CMT group had reduced prescription analgesic use, F = 6.123, p = .015, analgesic dependence, F = 14.322, p < .001, self-hate, F = 12.218, p < .001, negative urgency, F = 7.323, p = .006, and lack of perseverance, F = 7.453, p = .001, from baseline to postintervention, and those improvements were maintained at follow-up. The results show that exercises based on CMT principles and techniques and delivered online can reduce analgesic use, risk of analgesic dependence, and some aspects of self-criticism and impulsivity. (PsycInfo Database Record (c) 2020 APA, all rights reserved).