The current study examined whether the vocabulary skills of sequential bilingual children who learned Cantonese as a home language (L1) and English as a second language (L2) were predicted by the amount of L1 and L2 used at home. Ninety-two preschool children who learned Cantonese as L1 were recruited from a Head Start program. The amounts of L1 and L2 used at home were measured using parent questionnaires. Mixed patterns of L1 and L2 use were found across family members and home activities. After controlling for time spent in preschool, regression analyses showed that the amount of L1 and L2 used by individual family members, with the exception of older siblings, was not significantly linked to children's vocabulary skills. In contrast, the language used during some home activities such as dinner and book reading significantly predicted children's vocabulary knowledge. Implications for family involvement in facilitating children's vocabulary development are discussed.