The purpose of this study was to extend existing research relative to the predictors of early mathematics skills. Using Vygotskian theory as a framework, our primary goal was to determine whether social skills or letter awareness skills served as better mediators between receptive language and early mathematics concepts. The secondary goal was to examine possible differences in children's early mathematics, language, letter awareness, and psychosocial skills for two different childcare settings, centre and family childcare. Participants included 109 children (48 girls) all of whom attended out-of-home childcare at least 13 hours each week and who would be attending kindergarten the following year. Sixty-one children were enrolled in out-of-home family childcare and 48 in out-of-home centre childcare. Relative to our first goal, letter awareness fully mediated between receptive language and early mathematics (Sobel z-value = 2.92, p = 0.003). This suggested that when children are able to understand a system of symbols for sounds and if they have sufficient receptive language skills, they are able to understand a system of symbols for number. Teaching early mathematics skills as frequently as letter awareness skills might reinforce more efficient acquisition of both. Relative to our second goal, children in centre-based care outscored children in home-based childcare on early mathematics and letter awareness skills. This suggested that some differential trainings for centre childcare providers versus home care providers might be appropriate so as to provide the highest quality environment for both groups of children. (Contains 4 tables and 4 figures.)