Background Sinusitis is a common disorder associated with significant patient symptomatology that adversely affects quality of life. Sinusitis can cause further morbidity and mortality through its impact on comorbid disorders, progression of inflammation, and extension of infection. Objective This review highlights common complications of acute bacterial rhinosinusitis (ABRS) and chronic rhinosinusitis (CRS). Results ABRS is complicated by orbital infections, such as pre- or postseptal cellulitis, and by intracranial infections, including abscesses of the epidural and subdural spaces. CRS can contribute to asthma, sleep disordered breathing, and smell disorders. CRS can be complicated by development of allergic fungal rhinosinusitis or deformity of surrounding bony structures. Fungal complications contribute to morbidity and mortality. Conclusion Complications of ABRS, although relatively rare, can cause significant morbidity and mortality, and must be promptly recognized. CRS commonly complicates or drives comorbid diseases, which adversely impacts quality of life. Treatment of these complications often requires coordinated multidisciplinary care.