The Russian wheat aphid, Diuraphis noxia (Mordvilko), is a serious pest of cereal crops in the western United States. Therefore, the development of Russian wheat aphid-resistant cultivars is a high priority in many breeding programs of wheat, Triticum aestivum L. Understanding the type of resistance and its genetic control will aid in the timely development of Russian wheat aphid-resistant cultivars. This study was conducted to determine the inheritance of Russian wheat aphid resistance and the categories of resistance in STARS-225217 (a red winter wheat line selected from P1 225217). Crosses were made between STARS-225217 and the susceptible wheat cultivar ‘Chisholm’ F₁, F₂, and F₃ progeny were artificially infested with Russian wheat aphids in the greenhouse. F₁ data indicated that resistance is dominant, with no evidence of cytoplasmic effects. F₂ and F₃ data indicate that resistance in this line is controlled by a single gene; the F₂ showed a 3R:1S segregation ratio, and F₃ lines segregated in a 1R:2 Seg:1S ratio. Antibiosis and preference tests indicated that the STARS-225217 was not significantly different from the susceptible check. Tolerance tests indicated that STARS-225217 was significantly more tolerant to Russian wheat aphid feeding than the susceptible check for all parameters tested. Therefore, tolerance to Russian wheat aphid appears to be the most highly expressed category of resistance in STARS-225217 and it is controlled by a single dominant gene.