We present a simple and efficient method for the preparation of hemin‐modified SnO2 films on low cost, flexible, conducting ITO‐PET substrates to enable the development of a sensitive electrochemical sensor for the determination of H2O2. Using a hydrothermal processing method meant that the SnO2 films can be prepared at low temperatures, compatible with the PET substrate. The properties of the electrodes enable a high hemin loading to be achieved in a stable and functional way, allowing the direct reduction and oxidation of the immobilized hemin and maintaining its high electrocatalytic activity in the reduction of H2O2 on the surface. The results showed a sensitive response linearly proportional to the concentration of H2O2 in the range 1.5 to 90 μM.