Failure of pancreatic β cells to compensate for insulin resistance is a prerequisite for the development of type 2 diabetes. Sustained elevated circulating levels of free fatty acids and glucose contribute to β-cell failure. Selective inhibition of Histone deacetylase (HDAC)-3 protects pancreatic β cells against inflammatory and metabolic insults in vitro. Here we tested the ability of a selective HDAC3 inhibitor, BRD3308, to reduce hyperglycemia and increase insulin secretion in an animal model of type 2 diabetes. At diabetes onset, an ambulatory hyperglycemic clamp was performed. HDAC3 inhibition improved hyperglycemia over the study period without affecting weight gain. At the end of the hyperglycemic clamp, circulating insulin levels were significantly higher in BRD3308-treated animals. Pancreatic insulin staining and contents were also significantly higher. These findings highlight HDAC3 as a key therapeutic target for β-cell protection in type 2 diabetes.