Hormonal stimulation in common carp is a routine practice to enhance sperm production and control gamete maturation. This study aimed to compare the proteome of carp seminal plasma between control and Ovopel-induced males using two-dimensional differential in-gel electrophoresis. Ovopel induction increased sperm volume, total sperm count, seminal plasma osmolality, and pH and decreased seminal plasma protein concentration. In total, 36 spots were identified (23 up- and 13 downregulated), corresponding to 23 proteins differentially abundant in seminal plasma after Ovopel induction (p < .05; fold change 1.2). The majority of proteins were associated with the immune and stress responses including the transport protein (hephaestin), antiproteases (fetuin, α2-macroglobulin, TIMP2), complement components (C3, complement factor B/C2A), regulator of the coagulation cascade (plasminogen), modulators of the innate immune response, such as intelectin, ApoA and ApoE, and the cathepsin/cystatin system, and stress response (enolase1). In addition, hormonal stimulation seems to be related to the proteins involved in lipid metabolism, signal transduction, and tissue remodeling. Our results suggest that hormonal stimulation is not just concomitant with the hydration of testis but also induces the synthesis and secretion of seminal plasma proteins involved in sperm maturation and protection against stress induced by administration of the exogenous hormone. SIGNIFICANCE: It is well known that hormonal stimulation of male fish induces the final maturation of spermatozoa. However, molecular and biochemical basis underlying hormone-induced changes in semen is unknown at present. This study for the first time reveals, using proteomic approach, that hormonal stimulation in addition to hydration of testis is accompanied by significant changes in seminal plasma proteins related mainly to immune and stress response, lipid metabolism, signal transduction and tissue remodeling. These changes are associated with gene expression and synthesis and secretion of seminal plasma proteins by reproductive tissues. Overall, our results provide a framework for understanding the molecular mechanism responsible for hormonal stimulation in the reproductive tract of fish males.