In this study, we estimated insulin sensitivity and determined plasma concentrations of total-, low-molecular-weight (LMW), and high-molecular-weight (HMW) adiponectin and leptin in 72 domestic shorthair, neutered, client-owned cats. Glucose tolerance was assessed with an intravenous glucose tolerance test and body fat percentage (BF%) was measured with dual-energy x-ray absorptiometry. Total adiponectin was measured with 2 different ELISAs. Low-molecular-weight and HMW adiponectin plasma concentrations were determined by Western blot analysis after sucrose-gradient velocity centrifugation, and the adiponectin multimer ratio [SA = HMW/(HMW + LMW)] was calculated. Differences in glucose tolerance, leptin, total adiponectin, and multimer ratio among lean (BF% <35; n = 26), overweight (35 <BF% <45; n = 28), and obese (BF% >45; n = 18) cats as well as between male (n = 34) and female (n = 38) neutered cats were evaluated by linear regression and 2-way ANOVA. Sex and age were included as covariates for analysis of BF%, whereas BF%, fat mass, and lean body mass were covariates for analysis of sex differences. Increased BF% was negatively correlated with multimer ratio (SA, r = −45; P < 0.002), whereas no differences were found in total adiponectin concentrations among BF% groups (P > 0.01). Male cats had indices of decreased insulin tolerance and significantly lower total adiponectin concentrations than did female cats (mean ± SEM, 3.7 ± 0.4 vs 5.4 ± 0.5 μg/mL; P < 0.02). Altered SAs could contribute to an obesity-associated decreasing glucose tolerance in cats, and low total adiponectin concentrations may relate to increased risk of diabetes mellitus in neutered male cats.