Print-light-synthesis is a new concept for the large-scale in situ fabrication of nanoparticles and structures on large substrates. Here, Pt nanoparticles are synthesized on indium tin oxide (ITO) coated glass slides by using combined inkjet printing and photonic curing operated under ambient conditions and with low material usage. A formulated chloroplatinic acid based ink provides stable and reproducible jetting, optimized ink–substrate interaction and fast ink drying to create well-defined thin precursor films acting as nanoreactors. The precursor loading is precisely controlled by the printing parameters. Then, a short light pulse from a Xe flash lamp fully converts the printed Pt precursor containing film into pure Pt nanoparticles. The optimum precursor coverage is ≈1 µg mm−2 Pt consuming as less as ≈50 nL mm−2 of ink. Neither reducing nor capping agents are used resulting in pure Pt nanoparticles (30 nm average size) and micrometer-size aggregates. The nanostructures are well-adhered to the ITO substrate and show a stable electrochemical performance for the oxygen reduction reaction. The fast and cost-effective process optimization in terms of ink formulation, substrate pre-treatment, inkjet printing resolution, and post-processing for the rapid fabrication of Pt nano- and microparticle-coated ITO electrodes is presented and discussed.