Abstract In this research work, Pt/Al2O3 nanocatalyst was prepared in microemulsion system using γ-irradiation and chemical methods. In the first technique the reduction of platinum source was carried out using γ-irradiation, as a green procedure, at different dose from 10 to 80 kGy. In the second method, as a chemical method, NaBH4 was used to reduce platinum source to Pt nanoparticles. After preparing Pt nanoparticles stabilized in microemulsion system, γ-Al2O3 was added to obtain Pt/Al2O3 nanocatalyst by precipitation procedure. The final nanocatalysts products prepared by two techniques were also compared to each other. The resulted nanocatalyst samples were characterized by SEM and XRD techniques. The catalytic activity of the prepared nanocatalysts was also investigated in the liquid phase reduction of p-nitrophenol using a batch reactor as a reaction model. Interestingly, it is approved that these two chemical and non-chemical methods resulted the same final products of Pt/γ-Al2O3 nanocatalysts with almost the same catalytic activity. This report in the γ-irradiation method as a green technique may be considered a potential candidate in futuristic nanocatalyst fabrication field.