A novel hemoglobin (Hb) electrode modified with Au nanorods (AuNRs) and graphene oxide sheets (GOs) coated by polydopamine (Pdop) (GOs@Pdop) was fabricated and used for highly selective and sensitive determination of nitrite (NO₂⁻) and hydrogen peroxide (H₂O₂). The electrochemical characteristics of the sensor were studied by cyclic voltammetry and chronoamperometry. The GOs@Pdop composite was characterized by Fourier transform infrared (FTIR), ultraviolet-vis absorption spectroscopy (UV-vis) and transmission electron microscopy (TEM). The system was optimized to realize a reliable determination of NO₂⁻ at 0.7 V with a detection limit of 2.5 × 10⁻⁸ M and H₂O₂ at –0.2 V with a detection limit of 2.0 × 10⁻⁶ M (S/N = 3). The apparent Michaelis–Menten constants (K^app_M) were calculated to be 0.13 mM for NO₂⁻ and 0.70 mM for H₂O₂. Moreover, the sensor obtained from this study exhibited high sensitivity, good reproducibility, and long-term stability.