In this work, the effect of the addition of iridium on TiO2 and Nb2O5 supports obtained by wet impregnation method was evaluated in the photocatalytic degradation of 2,4-dichlorophenoxiacetic acid under UV irradiation. The synthetized materials were analyzed by different techniques in order to determinate their physicochemical properties. In general, it was observed that the addition of iridium modifies the surface area, band gap energy and it enhances the crystallinity of the materials. Besides, an increase in the photoactivity in the degradation of the herbicide was evidenced using the materials modified. However, the Ir/TiO2 photocatalyst possess the best photocatalytic behavior toward the degradation and possible mineralization of the herbicide. The improved performance of the photocatalyst could be argued by the role of the iridium particles as electron collectors favoring the effective separation of the charge carriers and, as consequence, increasing the degradation of the molecule.