Desmoplastic infantile ganglioglioma (DIG) is a rare supratentorial brain tumor, which is usually diagnosed before the age of two and has a favorable prognosis. To date, only a few cases have been reported in the literature. We report a case of DIG in a three-month-old boy who presented to our pediatric emergency department with decreased activity and excessive crying. This case report highlights the computed tomography (CT) and magnetic resonance imaging (MRI) findings of this rare tumor. Non-contrast CT scan findings in our case initially masqueraded as an extra-axial arachnoid cyst; however, the MRI findings after contrast agent administration were typical for the diagnosis of DIG.