The bidirectional relationship between disease activity and mental health in inflammatory bowel disease (IBD) has prompted investigations into the efficacy of psychotherapeutic interventions such as acceptance and commitment therapy (ACT) on biopsychosocial outcomes. We aimed to examine the efficacy of an ACT program (intervention) in comparison with a cognitive behavioral therapy-informed psychoeducation program (active control) for individuals with IBD and coexistent psychological distress. Both programs were delivered online through a hybrid format (i.e., therapist-led and participant-led sessions). A total of 120 adults with IBD were randomized to either the intervention (N = 61) or active control groups (N = 59). Efficacy was determined using linear mixed models for group differences, in rate of changes in study outcomes, between baseline, postintervention, and 3-month follow-up. The primary outcome health-related quality of life significantly improved in the intervention group when compared with the active control group, with a significantly different rate of change observed from baseline to postintervention ( t [190] = 2.15, P = 0.033) in favor of the intervention group with a medium effect size (β = 0.41, mean difference = 0.07, 95% confidence interval 0.01-0.12, P = 0.014). Similarly, the secondary outcome Crohn's disease activity significantly reduced in the intervention group when compared with the active control group, with a significantly different rate of change observed from baseline to 3-month follow-up ( t [90] = -2.40, P = 0.018) in favor of the intervention group with a large effect size (β = -0.77, mean difference = -9.43, 95% confidence interval -13.72 to -5.13, P < 0.001) ( P = 0.014). Furthermore, when observing the rate of change in outcomes over time for the groups separately, anxiety symptoms and pain significantly improved in the intervention group only, and conversely, ulcerative colitis activity and stress symptoms significantly improved in the active control group only. All other outcomes (N = 14) significantly improved over time in both groups including IBD activity, gastrointestinal unhelpful thinking patterns, visceral anxiety, fatigue interference, fatigue severity, fatigue frequency, psychological inflexibility, self-efficacy, resilience, current health status, depression symptoms, IBD control, and pain catastrophizing; however, these changes were not significantly different between the groups. Both programs were of benefit to people with IBD and distress. However, ACT offers a significant added benefit for health-related quality of life and self-reported Crohn's disease activity and may be a useful adjuvant therapy in integrated IBD care.