This study analyzes the interactional activity of code-switching between the Spanish and English languages in mother-child interactions. The data, drawn from video-recorded interactions of first-generation Latina mothers and their children, is analyzed using the methods of Conversation Analysis. Findings show that participants change codes to show their orientation to issues of epistemics by claiming (their own) lack of knowledge and negotiating epistemic status. First, participants code-switch to mark a lack of certainty or understanding, or rather, to present a K− epistemic stance. Second, participants switch codes to negotiate knowledge, as the language used by speakers orients to their epistemic status. This study contributes to our understanding of bilingual family interactions and the ways in which code-switching occurs in everyday interactions.