The basic helix-loop-helix (bHLH) transcription factors (TFs) gene family is an important gene family in plants, and participates in regulation of plant apical meristem growth, metabolic regulation and stress resistance. However, its characteristics and potential functions have not been studied in chestnut (Castanea mollissima), an important nut with high ecological and economic value. In the present study, 94CmbHLHswere identified in chestnut genome, of which 88 were unevenly distributed on chromosomes, and other six were located on five unanchored scaffolds. Almost all CmbHLH proteins were predicted in the nucleus, and subcellular localization demonstrated the correctness of the above predictions. Based on the phylogenetic analysis, all of theCmbHLHgenes were divided into 19 subgroups with distinct features. Abundantcis-acting regulatory elements related to endosperm expression, meristem expression, and responses to gibberellin (GA) and auxin were identified in the upstream sequences ofCmbHLHgenes. This indicates that these genes may have potential functions in the morphogenesis of chestnut. Comparative genome analysis showed that dispersed duplication was the main driving force for the expansion of theCmbHLHgene family inferred to have evolved through purifying selection. Transcriptome analysis and qRT-PCR experiments showed that the expression patterns ofCmbHLHswere different in different chestnut tissues, and revealed some members may have potential functions in chestnut buds, nuts, fertile/abortive ovules development. The results from this study will be helpful to understand the characteristics and potential functions of the bHLH gene family in chestnut.