Objective: Serotonin (5-HT) is a monoamine that has various functions in both neuronal and non-neuronal systems. 5-HT has been known as an anorexigenic neurotransmitter in central nervous system. However, accumulating evidences suggest that peripheral 5-HT may also affect organismal energy homeostasis. Here we demonstrate the role of adipocyte-derived 5-HT in the regulation of systemic energy metabolism. Methods: To generate the adipocyte-specific Tph1 KO (Tph1 FKO) mice, Tph1flox/flox mice were crossed with Adipoq-Cre mice. PBS or 300 mgkg-1 PCPA was administered as a daily intraperitoneal injection. To measure the metabolic rate, the mice were housed in open-circuit Oxymax/CLAMS system. To identify phenotypes in FKO and WT mice, we investigated IPGTT, ITT, H&E staining and gene expression in SCD or HFD condition. Results: The expression of tryptophan hydroxylase-1 (Tph1), the rate-limiting enzyme for 5-HT synthesis, and tissue 5-HT level were increased in white adipose tissue (WAT) when mice were fed with high fat diet. Pharmacological inhibition of 5-HT synthesis using Tph inhibitor suppressed the lipogenesis in epididymal WAT, induced beige adipogenesis in inguinal WAT and activated the adaptive thermogenesis in brown adipose tissue (BAT). Adipocyte-specific Tph1 KO (Tph1 FKO) mice exhibited similar phenotypes, suggesting the localized effects of 5-HT on adipose tissues. Tph1 FKO mice showed decreased body fat mass and increased energy expenditure, resulting in improved glucose tolerance. Ucp1 expression was also increased in stromal vascular fraction isolated from Tph1 FKO mice, which was abrogated by 5-HT treatment. Conclusion: These data suggest important roles of adipocyte-derived 5-HT in controlling energy homeostasis. Interestingly, blocking the synthesis of 5-HT in the fat induce more energy expenditure in the HFD than SCD.