Pancreatic exocrine insufficiency (PEI) is a common yet frequently under-recognised cause of maldigestion, malabsorption, and malnutrition. Although traditionally associated with primary pancreatic disorders such as chronic pancreatitis, cystic fibrosis, pancreatic cancer, or pancreatic surgery, it is now evident that PEI also occurs in a wide range of extra-pancreatic conditions and clinical settings. Advances in diagnostic testing and expanding clinical awareness have improved detection; however, significant misconceptions persist regarding when to suspect PEI; how to interpret diagnostic tests; and how to initiate, optimise, and monitor pancreatic enzyme replacement therapy (PERT). In everyday practice, these errors may lead to delayed diagnosis, inappropriate treatment, persistent symptoms, and preventable nutritional deficiencies. This “Mistakes in…” article highlights common pitfalls in the diagnosis and management of PEI, focusing on inappropriate reliance on faecal elastase testing, failure to recognise secondary causes, undertreatment with PERT, and inadequate nutritional assessment. By addressing these frequent mistakes, we aim to promote a more structured, patient-centred, and evidence-informed approach to PEI that improves clinical outcomes and quality of life.