Sexual dimorphism in reproductive strategies requires precise metabolic signaling. However, the mechanisms linking cellular communication to sex specific phenotypes remain poorly understood. Invertebrates with ancestral endocrine pathways may offer a useful evolutionary window into these foundational regulatory networks. Here, we utilize the echinoderm Apostichopus japonicus to investigate how extracellular vesicles (EVs) mediate sex-biased metabolic partitioning. EVs were isolated from mature gonads of both sexes. Through targeted metabolomics analysis of these gonadal EVs, we identified ten steroid-related metabolites showing profound sexual divergence. Female-derived EVs are preferentially enriched in upstream steroid precursors (including pregnenolone and DHEA sulfate) and multiple corticosteroids (cortisol, corticosterone, aldosterone, 11-deoxycortisol, 21-deoxycortisol), establishing a stable precursor reservoir essential for oogenesis and ovarian maintenance. In contrast, male EVs prioritize downstream androstenedione derivatives tailored for rapid functional responses during spermatogenesis. Multivariate analysis confirmed clear sex-specific separation of EV metabolic cargo, mapping directly onto highly conserved steroidogenesis and corticosteroid pathways. Collectively, our findings suggest that EVs may contribute to reproductive specialization by carrying sex-biased metabolic signals. By demonstrating that vesicular metabolite partitioning maintains distinct reproductive phenotypes in Apostichopus japonicus, this study provides a new mechanistic framework that may inform the evolution of sexual dimorphism in marine invertebrates.