A sensitive hydrogen peroxide (H2O2) biosensor was developed based on a reduced graphene oxide|carbon ceramic electrode (RGO|CCE) modified with cadmium sulfide-hemoglobin (CdS-Hb). The electron transfer kinetics of Hb were promoted due to the synergetic function of RGO and CdS nanoparticles. The transfer coefficient (α) and the heterogeneous electron transfer rate constant (ks) were calculated to be 0.54 and 2.6 s−1, respectively, indicating a great facilitation achieved in the electron transfer between Hb and the electrode surface. The biosensor showed a good linear response to the reduction of H2O2 over the concentration range of 2–240 µM with a detection limit of 0.24 µM (S/N=3) and a sensitivity of 1.056 µA µM−1 cm−2. The high surface coverage of the CdS-Hb modified RGO|CCE (1.04×10−8 mol cm−2) and a smaller value of the apparent MichaelisMenten constant (0.24 mM) confirmed excellent loading of Hb and high affinity of the biosensor for hydrogen peroxide.