Brown adipose tissue (BAT) is an adipose depot that utilizes fat to generate heat. In individuals with obesity, BAT accumulates excess lipids and becomes less efficient at thermoregulation and energy expenditure, exacerbating metabolic disease. Although unhealthy consumption habits can lead to obesity, genetic mutations can also increase the risk of obesity in humans. Genetic variants in a protein called ankyrin-B (AnkB), encoded by the ANK2 gene, have been shown to cause age-dependent obesity and type 2 diabetes in humans. Mouse models harboring these variants have AnkB deficiency in adipose tissues. Our previous studies revealed that loss of AnkB in white and brown adipose tissue led to insulin resistance and obesity due to AnkB’s role in facilitating GLUT4 endocytosis in white adipocytes. Still, the tissue-specific role of AnkB in BAT and its impact on metabolic health has yet to be uncovered. We investigated the consequences of AnkB deficiency on BAT lipid metabolism and age-related metabolic changes using 4-month-old and 10-month-old mouse models. Histological analysis of mice tissues reveals lipid accumulation in BAT of BAT-AnkB knockout (BAT-AnkB-KO) mice at both 4- and 10-mo mice cohorts with no changes in body weight. Interestingly, 10-month-old BAT-AnkB-KO mice exhibit changes in body composition with an increase in fat mass and a decrease in lean mass, demonstrating age-dependent adiposity. However, despite lipid accumulation in both age groups, young and older BAT-AnkB-KO mice can maintain normal thermogenesis and energy expenditure in response to cold exposure, suggesting that other compensatory mechanisms are at work. Through indirect calorimetry, we also discovered that there is an altered substrate preference from glucose utilization in young 4-month-old BAT-AnkB-KO mice to lipids in 10-month-old BAT-AnkB-KO mice. Glucose tolerance tests revealed that glucose sensitivity is improved in the young mice but is subsequently lost with age. Through insulin tolerance tests, we determined that insulin tolerance isn’t impaired, but 10-month-old BAT-AnkB KO mice have hyperinsulinemia. This phenomenon may result from the continuous presence of GLUT4 at the plasma membrane, leading to insulin resistance and the onset of diabetes. Finally, our data reveals that AKT2, the key effector molecule in the insulin signal transduction pathway, is decreased in the 10-month-old BAT-AnkB-KO mice providing further evidence of early insulin resistance. Taken together, these findings indicate the AnkB loss in BAT is sufficient to perturb insulin signaling, glucose homeostasis, and adiposity.