Background Acute diverticulitis (AD) is a common surgical condition classified as complicated or uncomplicated based on the severity of inflammation. Imaging findings, such as colonic wall thickening, may mimic or conceal malignancy. The incidence of colonic neoplasia is higher in complicated AD (7.8%–10.9%), making interval colonoscopy mandatory following complicated cases. The Association of Coloproctology of Great Britain and Ireland (ACPGBI) provides guidelines to standardize follow-up practices. Aim To evaluate adherence to ACPGBI guidelines for follow-up of conservatively managed AD within Cwm Taf Morgannwg University Health Board (CTM UHB). Methods The first audit cycle reviewed AD admissions at Princess of Wales Hospital (POWH) over 18 months to assess guideline adherence. Interventions included introducing a local management pathway, educational posters, and teaching sessions. A second cycle included data from POWH and Prince Charles Hospital (PCH) and was reviewed at a Trust Audit Meeting. Results In the first cycle at POWH, 55.6% of complicated AD cases had follow-up endoscopy, while 60% of uncomplicated cases underwent unnecessary endoscopy. The second cycle showed improvement: at POWH, follow-up for complicated AD increased to 62.5%, unnecessary endoscopies dropped to 27.3%, and malignancy follow-up remained 100%. At PCH, 57.1% of complicated cases had follow-up, but 66.7% of uncomplicated cases received unnecessary endoscopy. Conclusion Adherence to ACPGBI guidelines improved but varied across sites. Efforts should focus on reducing unnecessary investigations while ensuring proper follow-up for complicated and malignant cases.