We report systematic investigations of lattice mismatch strain and the strain relaxation induced modifications on the valence band electronic structure of the epitaxial Fe₃O₄/Si (100) and Fe₃O₄/MgO (100) heterostructures. The Fe₃O₄ films on Si (100) and MgO (100) substrates were investigated though the angle-integrated photoemission spectroscopy (AIPES) at room temperature in the energy range 45-65 eV. Depending on the strain state of the films, the Raman modes and the Verwey transition temperature show deviations from the corresponding bulk values. The valence band feature at 2.7 eV (3.5 eV) shifts towards (away) the Fermi level with an increase (decrease) in strain resulting in decrease (increase) of density of states (DOS) of the minority spin Fe(A) 3d-e_g band (majority spin Fe(B) 3d-t₂g band). The effect is more pronounced in the case of films on MgO (100) substrate in comparison to the films on Si (100) substrate.