In this work, the possibility for the simultaneous electrochemical determination of naproxen and paracetamol over the electrode, modified by conducting polymer composite with cobalt (III) oxyhydroxide, is analyzed for the first time. The correspondent mathematical model has been developed and analyzed by means of linear stability theory and bifurcation analysis. It has been shown that the electrochemical analysis of both substances may be easily conducted and interpreted at moderate electrode potentials. As for the oscillatory behavior, it is more probable than in the simplest cases due to the ionic forms' transformations during the naproxen determination and their impact on DEL capacitance