Early mathematics achievement sets the stage for a range of important academic and career outcomes. As efforts to improve elementary mathematics instruction have increased, efforts to better understand how students develop mathematics knowledge and why students respond to mathematics instruction have also emerged. Given known correlations between domain general skills and mathematics achievement, the current study explored the development of domain general skills and mathematics learning in the context of a mathematics intervention efficacy trial to better understand relations between academic gains and the development of domain general skills. This study examined the concurrent development of domain general skills and mathematics skills for 470 first-grade students at risk for mathematics difficulties in the context of a mathematics intervention study. Results indicated that although students demonstrated gains in domain general and mathematics skills, domain general skill gains were not statistically significantly associated with gains in mathematics achievement. In addition, students who received mathematics intervention did not demonstrate greater gains in domain general skills, despite the positive effect of mathematics intervention on mathematics skills. Implications for mathematics instruction, curriculum development, and future research are discussed. [This paper will be published in the "Journal of Educational Psychology."]