The palmaris longus muscle (PLM) is extremely variable both in number and form. We present the first reported case of three-headed reversed PLM in a 36-year old woman. The relevant literature is reviewed. Variations of the muscles of the forearm and specifically the PLM are not uncommon. However, different rates are given for the types and agenesis of PLM. In one study, the incidence of agenesis was 12.8% and other anomalies were 9%. 15 cases of reversed PLM have been reported in the literature. In our case, the three-headed PLM was resected. The patient's symptoms resolved and at 1-year follow-up she remains symptom-free.