Understanding the relationship between periodontal disease (PD) and systemic health (SH) is necessary for the accurate diagnosis and treatment of both. The aim of this study was to evaluate the knowledge of medical doctors in Turkey with regard to the association between PD and SH. This study was carried out using self-reported questionnaires that were sent to medical doctors who work at various universities and public and private hospitals in different cities in Turkey. The questionnaires consisted of questions about the demographic information of the medical doctors, as well as the knowledge of those doctors about the relationship between PD and SH. In total, 1,766 responses were received and 90.8% of the participants agreed that there was a relationship between PD and SH. Diabetes mellitus was the most frequent systemic disease (66.8%) known to be related to PD. Of the participants, 56.5% of the medical doctors referred their patients to periodontists for different reasons. Gingival bleeding was the most frequent reason for patient referrals, with 44% of doctors giving such referrals. Doctors who worked in basic medical sciences were significantly less aware of the relationship between PD and SH than the doctors in other specialties. Although the vast majority of the medical doctors reported that they knew the relationship between PD and SH, the findings of this study showed that this awareness was not supported by precise knowledge, and often failed to translate into appropriate clinical practice.