Chinese-English dual language learners (Chinese DLLs) are a growing population in the US. Existing studies of preschool-aged Chinese DLLs mostly focused on single-word vocabulary and rarely explored other skills important for school readiness. In the current study, we examined Chinese DLLs' development of receptive vocabulary and comprehension of semantic concepts (i.e. spatial and quantification expressions) in both English and Chinese (Mandarin/Cantonese) during a preschool year. Results indicated that while semantic concept comprehension in both English and Chinese showed significant growth during the year, only English, but not Chinese, receptive vocabulary showed a significant increase. Furthermore, DLLs' semantic comprehension, but not receptive vocabulary, showed cross-language transfer. Finally, the richness of DLLs' language experiences (e.g. frequency of book reading, multimedia exposure) at home was a significant predictor of Chinese DLLs' receptive vocabulary and semantic concept comprehension in the respective language. Supporting families to provide rich language experiences in both English and the home language may hold key to fostering successful dual language development.