Trust is integral to effective interprofessional collaboration. There has been scant literature characterizing how trust between practitioners is formed, maintained or lost. The objective of this study was to characterize the cognitive model of trust that exists between pharmacists and family physicians working in collaborative primary care settings. Pharmacists and family physicians who work collaboratively in primary care were participants in this study. Family health teams were excluded from this study because of the distinct nature of these settings. Through a snowball convenience sampling method, a total of 11 pharmacists and 8 family physicians were recruited. A semistructured interview guide was used to guide discussion around trust, relationships and collaboration. Constant-comparative coding was used to identify themes emerging from these data. Pharmacists and family physicians demonstrate different cognitive models of trust in primary care collaboration. For pharmacists, trust appears to be conferred on physicians based on title, degree, status and positional authority. For family physicians, trust appears to be earned based on competency and performance. These differences may lead to interprofessional tension when expectations of reciprocal trust are not met. Further work in characterizing how trust is developed in interprofessional relationships is needed to support effective team formation and functioning.