Although the peptide, exenatide, has been widely used as a drug for the treatment of type 2 diabetes, its short plasma half-life requires frequent subcutaneous injection, resulting in poor patient compliance in addition to side effects such as infection at the sites of injection. Here, we report a novel long-acting fusion peptide comprising exenatide and a human serum albumin (HSA)-binding aptide. A phage display screen of a library of aptides, yielded an HSA-specific aptide (APTHSA) that bound HSA with a Kd of 188 nM. The recombinant fusion peptide comprising exenatide and APTHSA (exenatide-APTHSA) was expressed in Escherichia coli and purified by affinity and size-exclusion chromatography. The resulting exenatide-APTHSA fusion peptide showed glucose-induced insulin secretion activity similar to that of native exenatide when tested in vitro using the INS-1 cell line. A pharmacokinetic analysis of exenatide-APTHSA after subcutaneous administration revealed a 4-fold longer plasma half-life (1.3 vs. 0.35 h) compared with exenatide. Furthermore, exenatide-APTHSA showed significantly improved anti-hyperglycemic effects in oral glucose tolerance tests and enhanced hypoglycemic effects compared with exenatide in a db/db type 2 diabetes mouse model. These results suggest that the exenatide-APTHSA fusion peptide could be used as a potential anti-diabetic agent for the treatment of type 2 diabetes.