Fe26.7M26.7Ga15.6Mn20Si11 (M=Co, Ni) high entropy alloy (HEA) thin films were prepared using a thermal evaporation method. The structural, magnetic, electrical and magnetoresistance properties of FeMGaMnSi amorphous HEA thin films were investigated to determine the effects of Co and Ni substitution and annealing. The amorphous structure of Fe26.7Co26.7Ga15.6Mn20Si11 and Fe26.7Ni26.7Ga15.6Mn20Si11 HEA thin films was confirmed by the XRD patterns. The HEA thin film thicknesses were measured to be 82.3 nm using an optic profilometer. The HEA with Co content relatively exhibits high saturation magnetization (1538 emu/cm(3)) value at room temperature. The electrical resistivity (rho) of the Fe26.7Ni26.7Ga15.6Mn20Si11 increases from 48 to 425 mu Omega cm with the annealing process at room temperature. The best magnetoresistance (MR) was obtained to be 105% at 300 K under an applied field of 1 T for the Fe26.7Ni26.7Ga15.6Mn20Si11 HEA thin film.