Background: The flowering transition is a critical process determining the onset of reproductive development and fruit production. The molecular mechanisms underlying this process in coconuts are poorly understood; however, recent studies have identified CnHd3a as a potential regulator of the floral transition in coconuts. Methods: In this study, we characterized the molecular structure of CnHd3a and analyzed its alternative splicing forms in tall and dwarf varieties of coconut palms during the flowering transition. We used qRT-PCR to measure the expression levels of CnHd3a at different developmental stages. Results: CnHd3a was expressed in leaves and the shoot apical meristem (SAM) during the flowering transition in both coconut varieties and flower tissues during flower development. Interestingly, the expression levels of complex isoforms of CnHd3a were higher in the leaves of dwarf coconuts than in those of tall coconuts, suggesting their involvement in shortening the vegetative growth phase of dwarf coconuts. The gene structure of CnHd3a was found to be conserved across different plant species, indicating the evolutionary conservation of the floral transition process. Conclusions: Our findings provide insight into the molecular mechanisms underlying the floral transition and flower development processes in coconut palm. The tissue-specific expression patterns of CnHd3a isoforms show their potential roles in growth and development. Further investigations focusing on the functional characterization of CnHd3a isoforms will have practical implications for coconut breeding and cultivation strategies.