<p>In recent years, metallic nanoparticles have emerged as promising agents for improving plant tissue culture. This study aimed to evaluate the effects of cobalt nanoparticles (Co-NPs) at different concentrations on key stages of in vitro propagation in purple passion fruit (<i>Passiflora edulis</i> Sims), focusing on morphogenesis, shoot growth, rooting, and acclimatization. During the morphogenesis stage, thin cell layer explants cultured on medium supplemented with Co-NPs showed enhanced callus and shoot induction, with the highest rates at 0.3 mg L⁻¹. When combined with 1.5 mg L⁻¹ BA, Co-NPs significantly increased the shoot induction rate (66.67%) compared to the control (51.11%). For shoot growth, Co-NPs alone at 0.3 mg L⁻¹ significantly enhanced shoot height, leaf number, and SPAD index, while reducing ethylene accumulation and stress-related hormones. The combination of Co-NPs with 1.0 mg L⁻¹<i> meta</i>-Topolin further enhanced shoot growth and development. Endogenous hormone analysis revealed that Co-NPs modulated the levels and ratios of auxin, cytokinin, gibberellin, and abscisic acid, contributing to improved organogenesis and shoot growth. In the rooting stage, Co-NPs combined with 2.5 mg L⁻¹ IBA improved rooting rate (up to 86.67%), root number (5.33 roots/shoot), and reduced callus formation at the shoot base. In the acclimatization phase, plantlets derived from Co-NPs treatments, especially at 0.2 mg L⁻¹, showed enhanced survival (97.78%), reduced defoliation, and vigorous growth. However, higher Co-NPs concentrations induced phytotoxic effects, including shoot tip necrosis. These findings suggest that Co-NPs, at optimized concentrations, could significantly enhance in vitro propagation efficiency and plantlet quality in purple passion fruit.</p>