Neuroendocrine system plays major roles in controlling physiology and behavior in insect. Adipokinetic hormone (AKH) is known for its function regulating energy homeostasis. We examined the AKH signaling in a coleopteran insect Tribolium castaneum. Mining the genome of T. castaneum we identified two putative genes encoding the AKH peptides and a G protein-coupled receptor orthologous to the AKH receptor of Drosophila. Specific interactions between the ligands and receptor were examined by using a heterologously expressed TcAKH-R in an aequorin reporter system. Two different AKHs, TcAKH-I and TcAKH-II, show significantly different degrees of activities with EC50 of 361 nM ad 47 nM, respectively, on the TcAKH-R reporter system. Real time reverse transcriptase PCR found that the TcAKH-R is expressed in the whole developmental stages, while the highest expression was found in late larval and early pupal stages. Tissue specific real time RT-PCR found the highest expression of the TcAKH-R in the central nervous system (CNS) implying possible novel neural functions of the AKH, whereas it is also expressed in the carcass of the insect including the fatbody as expected in its function for energy metabolism.