Whereas early childhood professionals can play a pivotal role in fostering young children's home language development, little is known about what determines the kind of multilingual parenting advice they offer families. The objective of this study was to deconstruct the processes culminating in two types of such recommendations: "advice highlighting the usage of the home language in the family domain versus advice to include the dominant language." Different theories, including Spolsky's insights on language policy and Ricento and Hornberger's Onion model, were used to investigate several aspects influencing professionals' interpersonal language policy. Logistic regression analyses were performed on a sample of 305 professionals employed at Flemish infant welfare clinics in Belgium. Our findings indicate that advice highlighting the home language is connected to manifold variables on the national, institutional, and interpersonal language policy levels. However, only few variables at the interpersonal and institutional level were associated with advice to include the dominant language. Hence, future research could further investigate the hitherto unidentified mechanisms underlying this type of advice. Overall, our results show the complex and nuanced ways in which the national, institutional, and interpersonal levels intersect in shaping different types of multilingual advice.