Nocturnists are the principal means by which hospital medicine groups currently ensure continuous overnight coverage of hospitalized patients within academic medical centers and community hospitals. Yet despite their involvement in most aspects of overnight care, a comprehensive review of the impact of nocturnists in the hospital is absent. Here we examine the physiologic effects of overnight work on clinicians, the quality of medical care delivered by nocturnists in floor and intensive care units, the impact of nocturnist presence on trainee supervision and graduated autonomy in academic settings, and prevalent staffing models. Nocturnists serve diverse roles across institutions, including performing overnight admissions and consultations, managing patients, supervising trainees, and participating in rapid response activations. Physiologically, nocturnists may experience circadian misalignment and sleep deprivation, which can impact cognitive function and results in potential long-term health risks to those working overnight. Studies show mixed results of nocturnist impact on patient outcomes, with comparative observational analyses revealing no significant differences in mortality, readmissions, or length of stay, despite perceived benefits. Nocturnist presence has been shown to enhance resident supervision and educational value of overnight rotations without compromising decision-making autonomy, though trainees' fear of revealing knowledge gaps persists. Overnight staffing models vary, with some institutions employing dedicated nocturnists and others using hybrid models; the heterogeneity of nocturnist responsibilities across institutions makes determining ideal models difficult. Compensation is typically greater for nocturnists, but the role's sustainability and impact on overall group retention remain unknown. Nocturnist programs are essential to provide continuous care of hospitalized patients and meet trainee supervision mandates, yet their full impact on patient and educational outcomes requires further investigation. Future research should aim to optimize staffing models to enhance patient care, trainee education, and clinician well-being.