The os intermetatarseum is located between the medial cuneiform and the base of the first and second metatarsals. Literature reviews have found few symptomatic cases of this condition since the 19th century. We report the case of a young female athlete, 20 years old, with sudden pain in the back of the midfoot after a jump. The os intermetatarseum is the rarest accessory bone in the foot and is typically asymptomatic. The presence of this bone should be considered when patients, especially young athletes, present with pain in the dorsum of the foot and compressive symptoms of the deep fibular nerve. Level of Evidence V; Therapeutic Studies; Expert Opinion.