To investigate the association of adiponectin gene polymorphisms and its levels with aneurysmal subarachnoid hemorrhages (aSAHs) prognosis. This case–control study enrolled 138 patients with aSAH and 102 healthy controls as case group and control group, respectively. Prognosis of case group was evaluated using Glasgow Outcome Scale. Polymerase chain reaction–restriction fragment length polymorphism was used to examine the genotypes of 45T>G and −11377C>G. Enzyme-linked immunosorbent assay was used to detect adiponectin levels. Logistic regression analysis was applied to assess the association of adiponectin gene polymorphism with aSAH prognosis. Case group had increased GG genotype and G allele genotype frequencies of 45T>G and −11377C>G compared with control group (all P < 0.01). In case group, TT genotype had the highest adiponectin level compared with both TG and GC genotypes (both P < 0.05). As for −11377C>G, GG genotype had the lowest adiponectin levels, followed by CG genotype and CC genotype in both groups (P < 0.05). In general, case group had decreased adiponectin levels compared with control group (P < 0.05). Univariate analysis showed that hypertension, Hunt–Hess grade, aneurysm size, aneurysms multiplicity and −11377C>G were associated with aSAH prognosis, while multivariate logistic regression analysis confirmed that hypertension, Hunt–Hess grade, residual flow in aneurysms and aneurysm size were independent risk factors for aSAH prognosis. Decreased adiponectin levels may be a pathological index for aSAH, which may be explain by the G allele of −11377C>G in adiponectin. Moreover, hypertension, Hunt–Hess grade, residual flow in aneurysms and aneurysm size may be independent risk factors for aSAH prognosis.