The posteromedial thigh (PMT) flap has been described for breast reconstruction in vertical fashion (vPMT). However, it might not incorporate enough soft tissue for reconstruction of a medium size breast. Here, we present a case utilizing the free inverted-L posteromedial thigh (L-PMT) flap for autologous reconstruction of the breast. A 65-year-old woman with a body max index (BMI) of 24.5 kg/m2 underwent nipple sparring mastectomy and received immediate unilateral breast reconstruction. The flap was raised based on the first medial perforator of the profunda femoris artery (PFA). The internal mammary artery and vein were dissected as recipient vessels. The flap size was 25 cm × 25 cm. The mastectomy specimen and weight of the flap was 260 g and 310 g, respectively. The flap survived completely after surgery. The donor site was primarily closed with minimal morbidities. Follow-up observations were conducted from 1 to 6 months. The patient was satisfied with the reconstruction. The free L-PMT flap may be suitable for breast reconstruction in women with moderate breast size. The inverted-L pattern of the PMT flap allows the surgeon to include a bigger quantity of flap soft tissue enabling a more anatomical shape of the breast and represents an alternative design that may be used for autologous breast reconstruction in selected patients.