Mn substituted Bi_0.90Ho_0.10FeO₃ (BHFO) thin films having the compositions Bi_0.90Ho_0.10Fe_1−xMn_xO₃ (BHFMO) (x = 0, 0.01, 0.03, 0.05) were synthesized via chemical solution deposition. The influence of the Mn dopants on the structure and multiferroic properties of the Bi_0.90Ho_0.10FeO₃ thin film is systematically investigated. X-ray diffraction, Rietveld refinement and Raman spectra analysis reveal that the crystal structure of the BHFMO thin film is rhombohedral (R3c:H + Rm:R). More importantly, the percentage of the space groups R3c:H and Rm:R is changed with the substitution of Mn into the Fe-site in the BHFO thin film, which indicates the presence of a structural transition in BHFMO. (X-ray photoelectron spectroscopy) XPS analysis confirms that (Ho, Mn) co-doping decreases the oxygen vacancy concentration, showing less Fe²⁺ ions in the co-doped BHFMO thin films compared with the BHFO thin film. The leakage current of the BHFMO_x=0.01 thin film is 5.398 × 10⁻⁴ A cm⁻² at 400 kV cm⁻¹, which is reduced effectively compared with BHFO (2.63 × 10⁻³ A cm⁻²). Well saturated hysteresis loops with a large remanent polarization of ∼80 μC cm⁻² in the BHFMO_x=0.01 thin film is observed, due to the reduced leakage current and the structural transition. The BHFMO_x=0.01 thin film also shows enhanced ferromagnetism with saturated magnetization (M_s = 5.24 emu cm⁻³) due to the destruction of the antiferromagnetically ordered spins arising from a structural transition.