Transition-metal-substituted manganese ferrites, Mn0.95M0.05Fe2O4 (M: Co, Cu, and Zn), with a single-phase cubic spinel structure, were synthesized using the combustion method. A high specific surface area (SABET) of 107 m2 g−1, along with pore size distribution (1.7 and 3.4 nm), was obtained for Mn0.95Zn0.05Fe2O4. All the synthesized ferrites exhibited significant hydrazine oxidation (HzOR) activity, and mass‑loading optimization revealed that their performance correlated with increasing SABET in the following order: Mn0.95Zn0.05Fe2O4 > Mn0.95Co0.05Fe2O4 > Mn0.95Cu0.05Fe2O4 > MnFe2O4. Importantly, Mn0.95Zn0.05Fe2O4 demonstrated fast kinetics for HzOR with a low Tafel slope of 193 mV dec−1 and an electron transfer coefficient of 0.31. Further, it delivers a high current density of 115 mA cm−2 with mass loading of 0.96 mg for HzOR. The Mn0.95Zn0.05Fe2O4 electrocatalyst exhibits the lowest onset potential of 0.65 V vs. RHE compared to other synthesized electrocatalysts. The double-layer capacitance (Cdl) of 0.49 mF cm−2 corroborates a higher SABET and porous microstructure of Mn0.95Zn0.05Fe2O4. DFT study reveals that the potential‑determining step (*N2H3 → *N2H2) has the lowest free‑energy barrier with a low limiting potential of 0.19 V for Mn0.95Zn0.05Fe2O4. The low barrier arises from Zn substitution, which moderates N2H3 adsorption, stabilizes intermediates, and enhances HzOR activity.