Despite limited reports on the specific effects of neem bioactive constituents in rodent models, the present study investigates the in-vitro influence of nimbolide, a tetranortriterpenoid derived from neem leaves on sperm functional, biochemical, and molecular events associated with capacitation in epididymal sperm. Sperm were incubated with nimbolide for 1-5 h, and capacitation-dependent parameters were evaluated along with immunoblotting and immunolocalization of protein tyrosine phosphorylation (PYP). Results demonstrated a dose- and time-dependent reduction in sperm motility, motility score, and sperm motility index, accompanied by decreased capacitation- associated molecular events, spontaneous acrosome reaction (AR), and reduced binding of cauda epididymal sperm to the zona pellucida. Immunoblot analysis revealed inhibition of tyrosine- phosphorylated proteins in the range of ~29–120 kDa, while immunocytochemical studies localized hypo-PYP states to the peri-acrosomal region and flagellar mid-piece. Biochemical assays indicated significant reductions in antioxidant enzymes including superoxide dismutase, catalase, glutathione reductase, and glutathione peroxidase, along with elevated hydrogen peroxide production and lipid peroxidation, suggesting nimbolide-induced oxidative stress. These alterations were associated with impaired energy metabolism and reduced levels of ATP, Ca²⁺, and cAMP, indicating disruption of the cAMP-PKA signaling pathway critical for capacitation. Collectively, nimbolide effectively suppresses sperm function by modulating tyrosine phosphorylation and oxidative status, leading to reduced AR and fertilization potential. These findings highlight nimbolide as a promising plant-based, non-hormonal male contraceptive candidate with reversible antifertility potential. The study also provides insights into sperm- associated signaling during capacitation and AR, supporting the development of safe, affordable, and next-generation neem-based contraceptive formulations.