Teacher and librarian collaboration is a main theme in school librarianship, education research, and professional literature. Now, within the American Association of School Librarians' "National School Library Standards," collaboration is one of the six Shared Foundations on which the standards are based. Improving collaboration in schools, and particularly collaboration between teachers and the school librarian, is of benefit to students both directly and indirectly, and helps improve student academic achievement. Developing trust is the first step toward building effective working relationships with colleagues. Librarians must build and maintain trust with the members of the school community, including parents, students, administrators, and teachers. This article discusses the following steps school librarians can take to help build or maintain trust among their colleagues: (1) Communicate effectively and consistently; (2) Build awareness of each other's knowledge base, and set boundaries to determine who knows what; and (3) Fulfill promises, and be careful about making commitments.