Mössbauer spectroscopy and X-ray diffraction measurements were performed to probe the magnetic properties of Fe_1-xCo_xSi (0 ≤ x ≤ 0.8) compounds at room temperature. X-ray diffraction measurements showed that the crystal structures of the synthesized samples existed as a single phase for all concentrations. Fittings of the Mössbauer spectra revealed that the family of Fe_1-xCo_xSi are weakly ferromagnetic for 0.1 ≤ x < 0.5 and completely lose their magnetic properties when x ≥ 0.5.