Alstroemeria (Alstroemeria × hybrida) is regarded as one of the world’s top ten commercially important and popular cut flowers and has been among the most successful cut flower crops over the past decade. One major challenge for this species is the decline in quality from harvest to marketing and export. In the present study, we evaluated the effects of silver nanoparticles synthesized from Moringa leaf extract at concentrations of 10, 15, and 20 mlL⁻¹, combined with 3% sucrose, and a control treatment (distilled water), on the postharvest traits of cut Alstroemeria cv. Red Sensation. The experiment used a factorial arrangement in a completely randomized design with three replications in 2024. The evaluated traits included fresh flower weight, floret diameter, electrolyte leakage, water uptake, total soluble solids, total sugar content, total chlorophyll, anthocyanin content, and the activity of the enzymes ascorbate peroxidase and catalase. The results showed that treatment and time significantly affected fresh flower weight, floret diameter, electrolyte leakage, water uptake, and total chlorophyll at the 1% probability level. The 15 mlL⁻¹ concentration performed best for key postharvest traits, with the highest fresh flower weight, floret diameter, and water uptake. Moreover, the 15 mlL^-1 treatment also showed the highest total chlorophyll content. In contrast, the lowest electrolyte leakage occurred at 10 mlL⁻¹, and the highest anthocyanin content was also recorded at this concentration. For time-dependent traits, fresh flower weight peaked on day 9 at 25.83 g, while floret diameter peaked on day 3 at 33.68 mm. In addition, total soluble solids peaked on day 3 under the 15 mlL^-1 treatment (253.6 °Brix), and ascorbate peroxidase activity peaked on day 3 under the 20 mlL⁻¹ treatment (0.815 µmol). Overall, applying silver nanoparticles synthesized from Moringa leaf extract effectively improves the postharvest quality of cut Alstroemeria flowers.