Abstract Cubic half‐ and full‐Heusler compounds with respectively 18 and 24 valence electrons exhibit semiconducting behaviors according to the Slater–Pauling rule. In this work, a half‐Heusler‐like ZrRu 1.5 Sb semiconductor with the space group F 3 m is discovered based on the Slater–Pauling rule. The ZrRu 1.5 Sb compound has 21 valence electrons per chemical formula and each atom has six valence electrons on average, showing a p‐type conduction with a dimensionless thermoelectric figure of merit zT ≈0.2 at 973 K. By adjusting the Ru content, both p‐type ( x ≤ 0.5) and n‐type ( x > 0.5) semiconductors are realized in the ZrRu 1+ x Sb solid solution. Following this way, other half‐Heusler‐like semiconductors, such as ZrRu 1.30 Ni 0.10 Sb, ZrRu 1.40 Ni 0.05 Sb, and ZrRu 1.30 Ni 0.05 Sb, are also successfully designed and synthesized, demonstrating the effectiveness and practicality of our strategy to explore Slater–Pauling semiconductors. Furthermore, these half‐Heusler‐like semiconductors show promising potential as thermoelectric materials. The p‐type ZrRu 1.4 Sb and n‐type ZrRu 1.7 Sb samples have zT values of 0.38 at 973 K and 0.25 at 773 K, respectively, offering superior base materials for further optimizing their thermoelectric properties. The discovery of ZrRu 1.5 Sb‐based thermoelectric semiconductors demonstrates the great potential to design Slater–Pauling phases with exotic physical properties.