Semiconductor photocatalysis is a cost-effective and eco-friendly strategy for water treatment methods. Herein, an environmentally favorable approach was employed for the synthesis of Ag/SnO2 nanocomposites supported bentonite clay (Ag/SnO2@Bent) in the presence of Perovskia abrotanoides plant extract as a reducing agent. The synthesized photocatalyst was characterized using sophisticated techniques. The results indicated that the Ag/SnO2@Bent was properly synthesized and the Ag/SnO2 was well immobilized on the surface of Bent. The presence of Bent could improve the morphology and structure of the photocatalyst, thus providing excellent adsorption and photocatalysis performance to the nanocomposite. The fabricated nanocomposite was applied for photocatalytic degradation of crystal violet (CV) dye. An optimal dye degradation was attained after visible light irradiation for 30 min using 1 g L−1 of photocatalyst, pH 4 and dye initial concentration of 100 mg L−1. The results indicated that modification of Ag/SnO2 with bentonite increased the dye degradation efficiency from 75.1 to 97.2%. Further, the cyclic experiments showed the Ag/SnO2@Bent photocatalyst maintained good structural stability and reusability. The present study may provide an environmentally benign approach for fabricating visible-light responsive catalysts for water treatment.