[en] Highlights: • Phase-pure double perovskite La2Fe2-xCoxO6 was prepared. • Orthorhombic and trigonal structures were obtained depending on the ratio of Fe to Co. • La2Fe2-xCoxO6 is a new high Tc ferromagnetic semiconductor with tunable magnetic properties. • Theoretical ab initio calculations further support our experimental results. - Abstract: Double perovskite La₂Fe_2-xCo_xO₆ was prepared and studied. Orthorhombic and trigonal structures were obtained depend on the molar ratio of Fe to Co. Fe-rich sample demonstrate ferrimagnetic properties; with increasing content of Co, trigonal structure is favored and the net magnetic moment of sample decrease gradually to zero. Our experimental results were further supported by first-principle theoretical calculations and demonstrate that La₂Fe_2-xCo_xO₆ is a new high T_c ferromagnetic semiconductor with tunable magnetic properties and is thus a promising material for spintronics devices.