Sex differences in the regulation of arterial tone by perivascular adipose tissue (PVAT) have been previously reported. We have demonstrated that PVAT compensates vascular tone in a situation in which vascular dysfunction occurs in mesenteric arteries of male SHRSP.Z-Lepr^fa/IzmDmcr (SHRSP.ZF) rats, an animal model of metabolic syndrome (MetS). However, such compensation function disappears in the late stage of MetS. In this study, we aimed to compare the effects of PVAT on arterial tone regulation between sexes and investigate the underlying mechanism. Ring preparations of superior mesenteric arteries, with and without PVAT, from 23-week-old male and female SHRSP.ZF rats were prepared. Vasodilation with acetylcholine and apelin mRNA levels were determined using the organ bath method and quantitative real-time polymerase chain reaction assays, respectively. In the absence of PVAT, there were no sex differences in artery relaxation; however, in the presence of PVAT, female but not male rats had increased artery relaxation. In PVAT, apelin mRNA levels were higher in female than in male rats. Further, apelin levels were positively correlated with artery relaxation differences with and without PVAT. This study demonstrates that in female rats, PVAT has an enhancing effect on vasodilation, a function that appears to be impaired in age-matched male rats. Further, apelin may be involved in the maintenance of the favorable effects of PVAT in female rats.