Environmental pollution control technology has a great demand for detection systems, particularly for pesticides and phenolic compounds. Moreover, analytical systems are highly requested for the dual detection of different pollutants using the same platform. In that direction, a new, reliable, easy to use and disposable biosensor for the detection of catechol and chlorpyrifos is proposed. The designed biosensor with synergic properties between the high conductivity of iridium oxide nanoparticles, low-cost screen printed electrodes and the efficiency of tyrosinase shows broad linearity ranges for catechol and chlorpyrifos detection. Using this biosensor, very low limits of detection for catechol (0.08 µM) and chlorpyrifos (0.003 µM) are observed and recoveries of spiked tap and river water samples have also been studied showing very good recoveries.