The synthesis of robust transition metal nanoparticles (TMNPs) are still intensively investigated because of multiple up‐to date applications in catalysis, solar cells, nonlinear optics, biological labeling, nanoelectronics, medicine and energy storage devices. Here we report synthesis of tetrahydroxyphenylporphyrin (TPP‐OH)‐stabilized TMNPs (including AuNPs, AgNPs and PdNPs) by mixing TPP‐OH and simple commercial metal salt and followed by the addition of sodium borohydride at 0 °C. The as‐synthesized nanocomposites show high catalytic activity in the reduction of 4‐nitrophenol, a pertinacious pollutant occurring in industrial waste water. In addition, it is evident that a drastic absorption change has been observed in UV/Vis spectra, confirming that generation of hydroxyl radicals induced by AgNPs and further oxidized methylene blue (MB) to hydroxymethylene blue (MB‐OH). [ABSTRACT FROM AUTHOR]