Dyes are broadly utilized and therefore wastewaters discharged into rivers or public sewage treatment plants are extremely polluted. Thus, the current work aimed to study the kinetic for photocatalytic degradation of Basic Red 51 (BR51) dye in aqueous solution by green synthesized zinc oxide nanoparticles (ZnO NPs). The results revealed that the maximum degradation (98.40%) and chemical oxygen demand (COD) removal (98.08%) was recorded with 150 mg of ZnO NPs, pH 3 and 5 ppm of BR51. ZnO NPs showed high reusability of 95.73%. The photocatalytic degradation of BR51 follows pseudo first‐order kinetics, the apparent rate constants (Kapp) of solar photocatalytic degradation of BR51 were determined as 0.3798, 0.6066, 0.2747 and 0.1307 min−1 for 5, 10, 15 and 20 ppm of BR51 at optimum condition respectively. Phytotoxicity study confirms that the degraded products of BR51 are non‐toxic. This confers the possibility of applying green ZnO NPs for the treatment of industrial wastewaters containing dye pollutants to ensure the environmental sanitation for future generations.