Recent advances in 2D magnetism have heightened interest in layered magnetic materials due to their potential for spintronics. In particular, layered semiconducting antiferromagnets exhibit intriguing low‐dimensional semiconducting behavior with both charge and spin as carrier controls. However, synthesis of these compounds is challenging and remains rare. Here, first‐principles based high‐throughput search is conducted to screen potentially stable mixed metal phosphorous trichalcogenides (MM^′P₂X₆, where M and M^′ are transition metals and X is a chalcogenide) that have a wide range of tunable bandgaps and interesting magnetic properties. Among the potential candidates, a stable semiconducting layered magnetic material, CdFeP₂Se₆, that exhibits a short‐range antiferromagnetic order at T_N = 21 K with an indirect bandgap of 2.23 eV is successfully synthesized . This work suggests that high‐throughput screening assisted synthesis can be an effective method for layered magnetic materials discovery.