A ganglion is a fluid cyst with a myxoid matrix that arises close to the tendons and joints. Its occurrence inside a joint is rare. Among the various pathological conditions producing impairment of the knee function, ganglia of the cruciate ligaments are quite rare. It may be painful or asymptomatic. Some patients may have a trauma history. Ganglia may mimic intra-articular lesions like tears of the anterior cruciate ligament (ACL) or meniscus. Ganglia, though commonly arise from the ACL, can also arise from other structures such as the posterior cruciate ligament (PCL) or meniscus. Ganglia are typically treated by arthroscopic excision and debridement. We report a case of ganglion of the PCL in a 28-year-old man; the lesion was incidentally discovered during ACL reconstruction with double bundle (Rigid fix technique). The patient underwent arthroscopic excision of the ganglion. At the end of 1-year follow-up the patient was pain free; a full range of motion of his right knee was restored, and he returned to his preinjury sport activity.