Knowledge of how to effectively prevent suicide attempt (SA) in high suicide–risk patients who also misuse opioids is limited. In a subset of data from 36 participants with baseline opioid misuse in a randomized clinical trial testing adjunctive mindfulness-based cognitive therapy to prevent suicide among high suicide–risk veterans (n = 18 per treatment condition), MBCT-S reduced the likelihood of SA and acute psychiatric hospitalization over 12-month follow-up. Those in MBCT-S had a relative risk of 17% and 42% for SA and hospitalization (p = .09, .02), respectively, compared to those receiving enhanced treatment as usual (eTAU) alone. Rates of opioid misuse during follow-up were more than halved with the addition of MBCT-S to eTAU (p = .08). Meanwhile, among trial participants who did not misuse opioids (n = 104), RRs of 64% and 77% for SA and hospitalization (p = .28, .33), respectively, were found with MBCT-S compared to eTAU. An MBCT-S trial with greater power is warranted in this population.