The presence of retroauricular tenderness and erythema has always been closely linked to a diagnosis of acute mastoiditis (AM), a condition that has become less common over the years given the advent of antibiotics and pneumococcal vaccination. However, other etiologies such as retroauricular cellulitis can also present similarly. We present the case of a 10-year-old patient who presented with outward and downward protrusion of the left ear with retroauricular tenderness and erythema and was initially presumed to have a diagnosis of AM and admitted for intravenous antibiotic management. Imaging was negative for any evidence of AM, and in retrospect, the patient was diagnosed with retroauricular cellulitis secondary to acute otitis externa. Being familiar with this differential of retroauricular pain and tenderness can lead to more cost-effective patient care and a different approach with antibiotic management.