This study examined the development of emerging self-regulation (SR) skills across the preschool years and relations to academic achievement in kindergarten and first grade. SR skills of 403 low-income African American and Latino children were measured at 2&1/2, 3&1/2, and 5 years (kindergarten). Reading and math skills were measured at 5 and 6 years (first grade) using the Woodcock-Johnson. Transactional relations between SR skills and achievement outcomes were estimated with latent difference score models. Increases in set shifting predicted prospective increases in reading, but not math scores. Increases in simple response inhibition predicted prospective increases in math, but not reading scores. Application of these findings to early intervention programming and needed supports for school readiness and achievement are discussed.