Background <p>Pigs have long been employed as an animal model of gracilis flap. However, studies on the vascular anatomy of pig gracilis are rare and confusing. The objective of this study was to explore the vascular anatomy of the gracilis flap in pigs from the perspective of comparative medicine and flap research.</p> Methods <p>Twenty fresh specimens of porcine hindlimbs were infused with black-colored latex for anatomical research (<i>n</i> = 15) and harvesting of the gracilis flap (<i>n</i> = 5). The primary parameters included the anatomic variance, length, and diameter of the pedicle of the pig gracilis flap. Based on the anatomical observations, the harvesting of pig gracilis flap was conducted on five hindlimbs with special attention to the anatomical observation in each step.</p> Results <p>There were two pedicles into the pig gracilis flap: a thicker pedicle originated from the medial circumflex femoral artery (termed P1), and a thinner pedicle originated from the femoral artery (termed P2). P1 penetrates through the adductor (9/15,60%, Type A) or through the intermuscular septum between the adductor and the pectineus (6/15, 40%, Type B). The harvesting of the pig gracilis flap was performed in the supine position. In each step, both the intermuscular septum and the pedicle could be clearly observed.</p> Conclusions <p>The vascular anatomy of the gracilis flap in pigs was described using anatomical descriptions adapted to classic veterinary anatomy books, which closely matched that of its human counterpart. However, either the anatomical distinctions between the two or their anatomical variations should be considered.</p> Level of evidence <p>Not gradable.</p>