Parenting is a critical mediator of children's school readiness. In line with this theory of change, data from the randomized clinical trial of Smart Beginnings (tiered Video Interaction Project and Family Check‐Up; N = 403, treatment arm n = 201) were used to examine treatment impacts on early language and literacy skills at child age 4 years (nLatinx = 168, nBlack = 198, nMale = 203), as well as indirect impacts through parental support of cognitive stimulation at child age 2 years. Although results did not reveal direct effects on children's early skills, there were significant indirect effects for early literacy (β = .03, p = .05) and early language (β = .04, p = .04) via improvements in parental cognitive stimulation. Implications for interventions targeting parenting to improve children's school readiness beginning at birth are discussed.