There is a close relationship between serotonergic (5-HT) activity and anxiety. ErbB4, a receptor tyrosine kinase, is expressed in 5-HT neurons. However, whether ErbB4 regulates 5-HT neuronal function and anxiety-related behaviors is unclear. Here, using transgenic and viral approaches, we show that mice with ErbB4 deficiency in 5-HT neurons exhibit heightened anxiety-like behavior and impaired fear extinction, possibly due to an increased excitability of 5-HT neurons in the dorsal raphe nucleus (DRN). Notably, the chemogenetic inhibition of 5-HT neurons in the DRN of ErbB4 mutant mice rescues anxiety-like behaviors. Altogether, our results unravel a previously unknown role of ErbB4 signaling in the regulation of DRN 5-HT neuronal function and anxiety-like behaviors, providing novel insights into the treatment of anxiety disorders.