Calcifying aponeurotic fibroma (CAF) is an uncommon benign tumor and a locally aggressive fibroblastic lesion. It commonly affects the palmar side of the hand and fingers, and the soles of the feet. The typical clinical manifestations are known as a poorly circumscribed, slow-growing, and asymptomatic firm mass. Most CAFs usually reveal low to intermediate or isointensity on T1-weighted images, and strong heterogeneous enhancement. However, various signal intensities on T2-weighted images have been reported depending on the degree of hypocellularity or the amount of calcification or collagen within the tumor. This report provides the radiographic and MRI finding of CAF arising in uncommon site, the knee region, of a 19-year-old male who presented with a painful and palpable mass.