Research Findings: Engineering play is a new framework for understanding constructive block building as a design process. The current study examined associations between engineering play with wooden unit blocks and mathematics and spatial skills of children with and without disabilities. Participants included 110 preschoolers (44% female; 25% children with disabilities), ages 49–72 months (M = 58.47, SD = 4.46), from the Midwest United States. A confirmatory factor analysis resulted in one engineering play factor including six of the nine engineering play behaviors with good model fit. Correcting for nesting and controlling for demographic covariates in marginal regression models, there was a significant positive association between engineering play and spatial horizontal rotation skills, β = .19. Moderation analyses revealed a significant positive association between engineering play and geometry for children with disabilities, β = .28. Practice or Policy: Findings provide initial evidence that engineering play is related to mathematics and spatial development and may be an important educational approach for supporting cognitive skills and school readiness in typically developing children and children with disabilities. (author abstract)