Tumours consisting of a glandular component, either an adenoma or adenocarcinoma, and a carcinoid component are uncommon. These tumours can be differentiated into collision, composite or amphicrine tumours. Most cases reported in the literature were mixed adenocarcinoma-carcinoid tumours. To date, only four cases of mixed adenoma carcinoid tumours have been reported in the literature. This case report describes a unique case of collision adenoma-carcinoid tumour in the colon complicated by carcinoid syndrome in a 45-year-old woman who presented with a one-month history of diarrhoea and weight loss. She developed recurrence of the carcinoid component of the tumour four months after endoscopic resection. We conclude that carcinoid syndrome can occur in an adenoma-carcinoid tumour; however, the prognosis of this condition is uncertain.