A comparison of the performances of three hydrogen peroxide (bio)sensors, based on the use of modified glassy carbon electrodes (GCE), is reported. GCE was modified with carboxylated carbon nanotubes (c-MWCNT), graphene (GR), titanium dioxide nanoparticles (TiO2) and hexaammineruthenium chloride (RUT) for the sensor design. In biosensor construction, coupling agents N-ethyl-N′-(3-dimethylaminopropyl) carbodiimide and N-hydroxyl succinimide were used for the immobilization of horseradish peroxidase (HRP) onto TiO2–c-MWCNT–GR–RUT and TiO2–c-MWCNT–GR modified GCEs. The modified electrodes were characterized by scanning electron microscopy, atomic force microscopy, cyclic voltammetry and electrochemical impedance spectroscopy methods. Electrode composition and critical working conditions such as pH and applied potential were optimized. TiO2–c-MWCNT–GR–RUT/GCE and HRP/TiO2–c-MWCNT–GR–RUT/GCE exhibited better analytical performance than HRP/TiO2–c-MWCNT–GR/GCE in terms of detection limit and sensitivity. Moreover, TiO2–c-MWCNT–GR–RUT/GCE sensor showed a sensitivity for H2O2 reduction 1.96 times higher than achieved with HRP/TiO2–c-MWCNT–GR/GCE configuration. The (bio)sensors were also applied to the determination of H2O2 in a disinfector sample, and satisfied results were obtained.