Perivascular adipose tissue (PVAT) functions not only as a structural support but a paracrine organ. However, it is still not clear how PVAT affects the arterial tensions under the hypoxic insult. The role of PVAT in the hypoxia-induced responses was examined in phenylephrine (3 μM)-precontracted rat aortas by using the in vitro blood-vessel myography and pharmacological interventions. The hypoxic exposure for 2 hours caused two phases of relaxations in both PVAT-intact and denuded aorta rings. In the early phase, the aortic rings relaxed upon hypoxia to the maximal level, whereas a sustained reduction of the relaxation level was observed in the late phase. The hypoxia-induced relaxations were enhanced by Nω-nitro-L-arginine (a NOS inhibitor) and indomethacin (a COX inhibitor) in aortic rings without PVAT, but this enhancement was less obvious in PVAT-intact aortic rings. PNU 37883, a blocker of the KATP channel, significantly decreased the hypoxic relaxations in PVAT-intact and removed aortic rings to a similar level. In contrast, the hypoxic relaxation was not affected by iberiotoxin (a BKCa channel blocker) or 4-Aminopyridine (a KV channel blocker). Furthermore, PVAT-mediated relaxations were reduced by repeated hypoxic treatments in aortas. These results suggest that PVAT enhances the hypoxic relaxations in rodent aortas, and this enhancement is partly via the increased permeability of KATP channels.