Parental beliefs and parenting practices in early childhood are fundamental for the development of preschoolers' school readiness and executive functions. This study examined the role of socioeconomic status (SES), ethnicity, maternal self-competence, parental cognitive stimulation, and maternal supportive discipline as predictors of five-year-old preschoolers' school readiness and executive function abilities in 70 families of low-SES homes with a Chilean majority or indigenous Mapuche minority background in Chile. Additionally, the mediating role of parental beliefs and parenting practices between SES and school readiness or executive functioning respectively was investigated as suggested by the Family Stress Model. Results show that maternal supportive discipline predicted school readiness above and beyond SES and ethnicity. Furthermore, maternal supportive discipline mediated the relation between SES and school readiness, whereby higher SES positively affected maternal supportive discipline, which in turn had a favorable effect on school readiness. All other associations were non-significant. The outcomes highlight that parental involvement of culturally diverse families from low-SES backgrounds is important for children's cognitive development. School readiness of Chilean preschoolers from low-SES homes might possibly be improved by enhancing maternal sensitivity and positive behavioral control strategies. These parenting skills have the potential to mitigate the adverse effects of low-SES environments to some extent. The findings of this study inform interventions integrated into early childhood education programs. (c) 2021 The Author(s). Published by Elsevier Inc. This is an open access article under the CC BY license ( http://creativecommons.org/licenses/by/4.0/ )