Zinc ferrite (ZnFe 2 O 4 ) nanoparticles were synthesized in the presence of naturally available lemon juice.The synthesized zinc ferrite nanoparticles were characterized by FT-IR, XRD, SEM, EDX, and BET techniques. The zinc ferrite nanoparticles were used for the synthesis of 1H-pyrazolo[1,2-b] phthalazine-5,10-dione derivatives by one-pot coupling reaction of phthalhydrazide, aromatic aldehyde, and malononitrile under conventional re ux condition. This green synthetic approach offers important features like non-toxic substances, maximum yields with a short reaction time, and easy puri cation of a product. It is a highly e cient, cheap, and reusable nanocatalyst.