Salinity occurring in intensively used agricultural, industrialized, and urbanized areas is one of the main factors in soil degradation. The effect of silver nanoparticles (AgNPs) on plant growth under environmental stresses is still not fully understood. Two experiments were conducted on the response of Asiatic lilies to treatment with colloidal AgNPs. In Experiment I, the study aimed to evaluate the effect of treating 'Osasco' lily bulbs with colloidal AgNPs (0, 25, 50, 100, and 150 ppm) on growth, flowering, and bulb yield, as well as the production of bulblets. Compared with the control, the applied colloidal AgNPs at all concentrations caused an acceleration of flowering and an increase in bulb diameter and the fresh weight of the aboveground part of the plants and bulbs. In addition, treatment with colloidal AgNPs at concentrations of 100 and 150 ppm increased bulblets' number and fresh weight. In Experiment II, the effects of colloidal AgNPs (100 ppm) and NaCl stress (600 mM) on the growth parameters, assimilation pigment content, and chemical composition of 'Bright Pixi' lily leaves were evaluated. As a result of the application of colloidal AgNPs, plants flowered faster and had increased height, petal width, fresh bulb weight, bulb diameter, and several scales in the bulb. Under NaCl stress, plants had reduced fresh weight of the aboveground part and bulb, bulb diameter, number of scales in a bulb, and contents of assimilation pigments, nitrogen, potassium, calcium, and manganese. Colloidal AgNPs offset the adverse effects of salinity on bulb yield by increasing fresh bulb, bulb diameter, and the number of scales in lily bulbs. In conclusion, using colloidal AgNPs can contribute to developing new methods of bulbous plants production and an effective strategy to protect plants from ever-increasing land salinization.