To understand the role of serotonin 5-HT2A receptor (5-HT2AR) gene in the growth and development of the mussel Mytilus coruscus, we cloned the 5-HT2AR gene cDNA full length of M. coruscus through RACE technology and analyzed the temporal and spatial expression of this gene via the real-time fluorescent quantitative PCR (qRT-PCR). The full length of 5-HT2AR gene was 2 636 bp and 2 124 bp of open reading frame (ORF) encoding 707 amino acids. Homologous analysis of the amino acids of 5-HT2AR gene in M. coruscus shared high similarity with Homo sapiens (45%), Mus musculus (45%), Danio rerio (48%), Crassostrea gigas (49%) and Mizuhopecten yessoensis (67%), respectively. This study showed that 5-HT2AR mRNA expression was detected in all tissues and the highest expression was found in gill and female gonad, indicating that 5-HT2AR gene may play an important role in perception of the external environment and promotion of mature oocytes. The 5-HT2AR mRNA was expressed at all developmental stages, suggesting that 5-HT2AR gene may be involved in the regulation of the growth and development. Taken together, our findings may provide new insights into clarifying the function of 5-HT gene family in molluscs.