Paranasal sinus mucocoeles can be secondary to chronic rhinosinusitis and can result in intra-orbital and intra-cranial complications requiring surgical management. The natural history of conservatively managed mucocoeles is not well established. We aimed to quantify the proportion of radiologically identified paranasal sinus mucocoeles resulting in complications over 10 years. We retrospectively reviewed anonymised data on radiologically diagnosed mucocoeles between 2011 and 2021 at two UK hospitals. We collected data on age at presentation, extent of sinus involvement, management and complications. We identified 60 patients with mucocoeles, of which 35 (58%) were incidental findings from radiological investigations. The mean age was 58 years. Fifteen patients (25%) were managed surgically and one presented with recurrence following surgery. Overall, six patients (10%) had an intra-orbital extension of their mucocoele and three (5%) had an intra-cranial extension. There was no difference in the rates of intra-cranial extension between conservative and surgical cases but surgical cases included a higher rate of intra-orbital extensions (27% vs. 4%, p = 0.01). The proportion of patients requiring surgical intervention in this study is low. Incidental and asymptomatic mucocoeles have a relatively benign disease course and selected uncomplicated cases can be considered for conservative management with serial scanning at 12 months.