Rhinosinusitis affects many pediatric patients as well as 1 in 6 adults in any given year, resulting in ambulatory care, pediatric, and emergency department visits. Uncomplicated rhinosinusitis requires no imaging or testing and does not require antibiotic treatment. Using strict clinical diagnostic criteria may minimize unnecessary antibiotics. When indicated, amoxicillin with or without clavulanate for 5 to 10 days remains the first-line antibiotic, despite increasing incidence of staphylococcal sinusitis in the post-pneumococcal conjugate vaccine era. Emergency providers also need to recognize atypical cases in which uncommon but serious complications of sinusitis cause both morbidity and mortality.