Chronobiology and sleep medicine are pivotal disciplines for understanding human health. Additionally, the lack of training in medical schools exacerbates the underdiagnosis and undertreatment of sleep disorders. This study investigated the exposure of Brazilian medical students to chronobiology and sleep medicine during their undergraduate education and assessed their knowledge in these areas. The study was conducted between December 2021 and June 2022 through the administration of an online questionnaire (Google Forms) to medical students in the final two years of undergraduate studies. The questionnaire gathered student data (i.e., sex, age, and educational institution), research data (stage in the medical program with exposure to chronobiology or sleep medicine), and responses to a questionnaire on basic knowledge of sleep medicine and chronobiology (adapted from Assessing Sleep Knowledge in Medical Education - ASKME). A total of 240 students from medical schools in Brazil participated, 4.6% of whom reported no exposure to either subject, with exposure declining as students progressed through the curriculum. Only 3.7% reported specific disciplines covering these topics. Over half of the students encountered learning barriers, such as limited curriculum time. Despite these challenges, the accuracy rate in responses regarding chronobiology and sleep medicine was 79.75%, positively correlating with exposure level and knowledge retention. This study underscores the urgent need for enhanced education in sleep medicine and chronobiology within Brazilian medical schools. It offers insights into the current landscape of sleep medicine education in Brazil and lays groundwork for future efforts to integrate these essential subjects into medical school curricula.