Ectrodactyly, also known as split hand/split foot malformation, is a rare congenital disease defined as the absence or underdevelopment of the central digits with a median cleft of the hand or foot. It can be an isolated sonographic finding or associated with a syndrome. This case study describes isolated left-handed ectrodactyly diagnosed sonographically at 20 weeks gestation, during a routine anatomy sonogram. The patient had no family history of this condition, which demonstrates the importance of sonography for early diagnosis, counseling, and genetic testing options.