Cyclic voltammetric and electrochemical impedance spectroscopic results showed potentiodynamic deposition of a noble poly(aquachlorobis(1,10- phenanthroline)cupper(II)iodidemonohydrate) (poly(ACP2CuIH)) polymer film on the surface of glassy carbon electrode. In contrast to the unmodified glassy carbon electrode, poly(ACP2CuIH) film modified glassy carbon electrode (poly(ACP2CuIH)/GCE) in a solution containing equi molar mixture of theophylline and caffeine revealed well separated oxidative peaks with much enhanced peak current and reduced over-potential showing the electrocatalytic property of the polymer film towards the oxidation of theophylline and caffeine. Poly(ACP2CuIH)/GCE was used for square wave voltammetric simultaneous determination of theophylline and caffeine in various real samples including pharmaceutical tablets, tea, and human serum samples. Under optimized solution and square wave voltammetric parameters, oxidative peak current response of poly(ACP2CuIH)/GCE showed a linear dependence on the concentration of caffeine and theophylline in a reasonably wide range of concentration. The method showed exactly the similar sensitivity towards simultaneous theophylline and caffeine as does for their separate detection. The current response of poly(ACP2CuIH/GCE for simultaneous detection of theophylline and caffeine showed a linear dependence on the respective concentration in the range of 1–200.0 μM with a limit of detection of 8.92 × 10-9 M for theophylline, and 1.02 ×10-8 M for caffeine. The method was successfully used to detect theophylline and caffeine in tea (Black lion, Addis, and Wush wush), pharmaceutical tablet (Panadol extra and Theodrine), and human blood serum real samples with excellent recovery results of 97.0–102.0% and 95.4–96.8%, 99.0– 101.0 and 98.9–100.0, and 100.0–101.4% and 98.9–99.3%, respectively. The accuracy, selectivity, stability, and reproducibility results validated the developed method for its applicability for simultaneous determination of theophylline and caffeine in complex matrix real samples including tablet formulation, tea, and human blood serum samples