Background: Numerous studies have revealed that patients with irritable bowel syndrome (IBS) have emotions dysregulation and negative illness perception. Thus, the aim of this study was to explore the effect of program based on acceptance and commitment therapy (ACT) versus processing emotion regulation therapy (PERT) on illness perception and emotion regulation among IBS patients. An open-label randomized controlled trial design was applied at the Internal Medicine Outpatient Clinic in Zagazig University Hospitals, Egypt. A purposive sample included 52 patients suffering from IBS randomized into three equal groups: one group received ACT, the other received PERT, and control group. A self-administered questionnaire for studied patients covered three parts; demographic characteristics and clinical data of IBS patients, the Brief Illness perception questionnaire, and emotion regulation questionnaire (ERQ) were used to collect data. Results: There are no statistically significant differences between the studied groups in their demographic characteristics and history of disease pre compared post-interventions. There was a statistically significant decrease in illness perception and an increase in emotion regulation scores post-interventions compared to pre-interventions in both the ACT and PERT groups. However, there was no statistically significant difference in illness perception and emotion regulation scores among the control group pre- and post-intervention. Additionally, there was a strong statistically significant negative correlation between illness perception and emotion regulation scores pre- and post-interventions. Conclusions: The findings demonstrate positive effects of both ACT and PERT based programes on IBS patients' illness perception and emotion regulation. The PERT is more effective than ACT based program.