Despite a rapid growth in the number of dual language learning children (DLLs) in the United States, there is a limited understanding of what parents of DLLs believe and know about dual language learning and education, and how parental beliefs and knowledge relate to children's dual language experiences at home. In the current study, 225 parents of 0- to 6-year-old Spanish-English DLLs living in the United States reported on their beliefs and knowledge about dual language learning and education, children's Spanish and English exposure and usage, and children's engagement in learning activities in Spanish and English at home. Parents showed strongly positive beliefs about the benefits of home language/bilingual experiences. Nonetheless, they varied in their beliefs and knowledge about children's capability of learning two languages and the "detriments" of home language/bilingual exposure. These aspects of parental beliefs and knowledge differentially predicted children's dual language exposure and usage and engagement in learning activities in Spanish and English. These findings reveal the relation between parental beliefs and knowledge and children's dual language learning experiences and call for efforts to enhance parents' knowledge.