Purpose: The purpose of this study was twofold: (a) to describe how the language diversity (i.e., the within-group variability in dual-language skills) of Latino dual-language learner (DLL) preschoolers was related to their science readiness skills and (b) to describe the importance of language of science instruction for Spanish-dominant children. Method: Latino DLL children's (N = 161; ages 3-5 years) language skills were assessed in various domains of both Spanish and English, and then their science readiness skills were assessed in their dominant language. Using a latent profile analysis, profiles were generated to describe the diversity of DLLs' bilingual skills. These profiles were used as independent variables in a series of hierarchical regressions to predict children's science readiness skills. With the Spanish-dominant subsample, an interaction term was created between profile membership and language of science instruction to determine how language of instruction contributes to the relation between language and science readiness skills. Results: English-dominant children and children with high and balanced dual-language skills had the highest science readiness skills, and instruction in two languages was related to higher science readiness skills of certain Spanish-dominant children. Results underscore the linguistic heterogeneity of Latino DLL children and its importance for school success and bilingual instruction initiatives. Conclusion: Findings provide evidence for the within-group variability in the dual-language skills of Latino DLL preschool children relating to differences in their science readiness skills, as well as for how bilingual instruction is related to science readiness skill.