Density functional theory calculations are performed to investigate the electronic and magnetic properties of Fe3-x Cr (x) Si alloys with Cr concentration in the range of 0.25 a parts per thousand currency sign x a parts per thousand currency sign 2.75. The L2(1) phase is found to be a more stable one in comparison with the A15 phase for x a parts per thousand currency sign 1.50 beyond which the A15 phase becomes more stable. Alloys with the stable L2(1) phase are found to be metallic for x a parts per thousand currency sign 0.75, however, a half metallic behavior is found at x = 1.00, 1.25, and 1.50 with band gaps of 0.60, 0.24, and 0.21 eV, respectively. In contrast, all A15 structures are found to be metallic. The total magnetic moments are found to decrease for L2(1) phase from 14.4 mu(B)/cell at x = 0.25 to zero at x = 2.00 with non-integer values for the metallic structures and integer values for the half-metallic. However, a monotonic decrease is found for the case of A15 phase with values larger than those of L2(1) phase.