Objectives This study aimed to explore the challenges encountered during dietary decision-making among Chinese adults with inflammatory bowel disease (IBD) and provide a theoretical basis for developing targeted strategies to improve dietary decision-making ability. Design A descriptive qualitative interview study. Setting This study was conducted in four hospitals in Nanjing, China. Participants From June 2023 to July 2024, semi-structured interviews were held with 24 patients diagnosed with IBD across four hospitals in Nanjing through purposive sampling. Results Five themes and twelve sub-themes were identified. The five themes were as follows: (1) challenges in problem identification (insufficient perception of disease threat and excessive fear of flare-ups); (2) challenges in information integration (absence of individualised professional guidance and decision-making burden due to overwhelming information); (3) challenges in decision implementation (conflicts between dietary preferences and diet management, socialising and diet management, and limited choices and diet management); (4) challenges in post-decision reflection (disappointment and regret over decision outcomes and self-regulatory fatigue); and (5) other factors influencing dietary decisions (dietary decision dilemmas under inappropriate social support, avoidance of decisions under emotional influence, and Chinese cultural influences on dietary decision-making). Conclusion The results of this study showed that patients with IBD encountered various challenges that impeded healthy dietary decisions. Our findings provide a foundation for the future development of dietary decision-making support strategies. This study may provide a framework to guide the development of dietary decision-making aids tailored to the dietary challenges encountered at various decision-making stages, thereby promoting patients’ healthy eating behaviours.