Inflammatory bowel disease (IBD) has been vastly associated with the development of depression and it is thus considered that the mechanisms that underlie this link should be explored. The present study aimed to examine the longitudinal effects of IBD symptoms and a maladaptive emotion regulation process, experiential avoidance (defined as the tendency to attempt to control internal experiences), on depression symptoms. The sample comprised 116 IBD patients of both sexes that completed validated self-report measures on an online platform in three different times (equally spaced 9 months apart) during an 18-month period. Results demonstrated that IBD symptomatology at baseline was linked to experiential avoidance and depressed mood 9 and 18 months later. The level of experiential avoidance at baseline was also correlated with the subsequent experience of depression symptoms, 9 and 18 months later. Results also revealed that, although IBD symptomatology at baseline predicted depressive symptomatology 18 months later (β = 0.24; P = 0.008), when experiential avoidance at baseline was added to this model, this process became the only predictor of the outcome (β = 0.60; P < 0.001; R2 = 0.41). These results corroborate previous literature by indicating that IBD symptomatology may lead to depression symptomatology. Nevertheless, the current study additionally revealed that the engagement in experiential avoidance – that is, in attempts at controlling the frequency, form or intensity of internal experiences – might have a greater role on the determination of patients’ depressed mood than the experience of adverse physical symptomatology. Maladaptive forms of emotion regulation in IBD patients should be targeted to prevent depression symptoms.