ABSTRACT: Patient outcomes with hospitalist care have been studied in many settings, yet little is known about how hospitalist care interacts with trainee care to affect patient outcomes in teaching hospitals.The aim of this study was to compare patient outcomes between hospitalist-preceptors and hospitalists working alone (isolating the effect of housestaff involvement), and between hospitalist-preceptors and academician-preceptors (isolating the effect of attending type, given housestaff involvement).A four-year retrospective cohort study of patients (n?=?13,313) admitted to all internal medicine services at an academic medical center from July 2008 to June 2012.Using generalized estimating equations, we measured readmission within 30 days, hospital length of stay, cost of the index hospitalization, and cumulative cost including readmissions within 30 days.In the adjusted models, 30-day readmission odds were higher for academic-preceptors (OR, 1.14 [95% CI, 1.03?-?1.26]) and hospitalist-preceptors (OR, 1.10 [95% CI, 1.002?-?1.21]) than for hospitalists working alone. Compared with hospitalists working alone, academic-preceptors were associated with shorter length of stay (mean difference, 0.27 days [95% CI, 0.18?-?0.38]), lower index hospitalization costs (mean difference, $386 [95% CI, $192?-?$576]), but similar cumulative inpatient costs within 30 days of discharge. Compared with hospitalists working alone, hospitalist-preceptors were associated with shorter length of stay (mean difference, 0.34 days [95% CI, 0.26?-?0.42]), lower index hospitalization cost (mean difference, $570 [95% CI, $378?-?$760]), and a trend toward lower cumulative cost (mean difference, $1347 [95% CI, $254?-?$2,816]).Preceptor-led medicine services were associated with more readmissions within 30 days, shorter lengths of stay, and lower index admission-associated costs. However, when considering cumulative hospitalization costs, patients discharged by academician-preceptors incurred the highest cost and hospitalist-preceptors incurred the lowest cost.