A novel modified carbon paste electrode (CPE) based on an MnO2‐TiO2 nanocomposite and 2‐(3,4 dihydroxyphenethyl) isoindoline‐1,3‐dione (DPID) as the modifier for the simultaneous analysis of cysteine (Cys), tryptophan (Trp) and uric acid (UA), as three key biochemicals present in human body. The MnO2/TiO2 nanocomposite was synthesized through a chemical co‐precipitation approach and the resulting electrode (MnO2‐TiO2/DPID/CPE) was used for studying the electrochemical oxidation of cysteine (Cys), tryptophan (Trp) and uric acid. As opposed to conventional CPEs, the oxidation peak potential of cysteine on MnO2‐TiO2/DPID/CPE had a 600.0 mV decrease in overpotential and could be observed at 30.0 mV, and the signals were linear from 0.025 to 200.0 μM, and a lower detection limit of 0.013 μM was reached. The MnO2‐TiO2/DPID/CPE was satisfactorily used for the concurrent analysis of Cys, Trp and UA in pharmaceutical and biological samples.