There are few studies that focus on the referral behavior of primary care physicians (PCP), and there are none on Icelandic PCPs referral behavior. The purpose of this study was to examine factors contributing to Icelandic PCPs intentions to refer patients with mental health concerns to psychotherapy using variables from the Theory of Planned Behavior (TPB: Attitudes, Subjective Norms, Perceived Behavioral Control, Referral Intentions), referral history, and barriers to psychotherapy referrals. Path analyses were performed on data from 92 Icelandic PCPs to test two proposed models and an alternative post hoc model. It was found that PCPs attitudes towards psychologists mediated the relationship between cost of psychological services (Barrier 2) and intention to refer to psychotherapy and between PCPs urgency to treat patients presenting with mental health concerns (Barrier 3) and intention to refer. Furthermore, the cost of psychotherapy as a barrier was linked with PCPs perceived control over referral, and PCPs urgency to treat their patients was linked with subjective norms. This study extends the available literature on the TPB by demonstrating the usefulness of attitudes mediating the relationship between specific contextual elements that are important to the behavior under study and intentions.