Ulnar longitudinal deficiency(ULD) is a rare skeletal condition marked by the partial or complete failure of the formation of the ulna. This rare condition is often associated with fixed flexion deformity, radial head subluxation, complex carpal, metacarpal, and digital abnormalities. Most presentations are male-preponderant and right-sided. Different classifications have described ULD. Usually, the condition is not associated with systemic findings; however, detailed physical examination and radiologic evaluations are crucial for assessing and managing affected patients. We report a rare case of ULD in an 11-month-old female infant with congenital absence of the left ulna, four digits, and a postaxial hypoplastic finger.