Abstract Background Diet is associated with the onset of inflammatory bowel disease [IBD]. Up to half of IBD patients believe that diet contributes to flares. However, studies on this topic are sparse and merely focus on specific nutrients, food items or food groups. We aimed to analyse the association between dietary patterns and flare occurrence in two geographically distinct Dutch cohorts. Methods In this longitudinal study, 724 IBD patients [Northern cohort: n = 486, Southern cohort: n = 238] were included and followed for 2 years. Habitual dietary intake was obtained via semi-quantitative food frequency questionnaires at baseline. Principal component analysis [PCA] was conducted on 22 food groups to identify dietary patterns. Flare occurrence was analysed in 427 patients in remission at baseline, using multivariable Cox proportional hazards. Results Compared to the Southern cohort, patients in the Northern cohort were younger at diagnosis, comprised more females, and had lower overall energy intakes [all p < 0.05]. PCA revealed three dietary patterns explaining 28.8% of the total variance. The most pronounced pattern [explaining 11.6%] was characterized by intake of grain products, oils, potatoes, processed meat, red meat, condiments and sauces, and sugar, cakes and confectionery. Of the 427 patients, 106 [24.8%] developed an exacerbation during follow-up. The above dietary pattern was associated with flare occurrence (hazard ratio [HR]: 1.51, 95% confidence interval [CI]: 1.04–2.18, p = 0.029), as was female sex [HR: 1.63, 95% CI 1.04–2.55, p = 0.032]. Conclusions A dietary pattern, which can be seen as a ‘traditional [Dutch]’ or “Western’ pattern was associated with flare occurrence. Confirmation in prospective studies is needed.