Background: There is a lack of studies comparing hospitalization and post-hospitalization outcomes between internal medicine (IM) hospitalists and family medicine (FM) hospitalists. Objective: To compare the length of stay (LOS), hospital cost, and 30-day all-cause readmission rate among patients treated by IM hospitalists and FM hospitalists. Design and Setting: Prospective cohort study in a referral center. Propensity score matching was used to balance baseline characteristics between comparative arms. Participants: 747 patients 18 years and older who were admitted to hospitalist services. Intervention: Treatment by IM hospitalists and FM hospitalists. Main Measures: LOS, hospital cost, and 30-day all-cause readmission. Treatment arms were compared by two methods. We compared patients who were seen by FM exclusively with those treated exclusively by IM services. Covariate adjusted differences in outcomes were estimated by multivariable regression. For a secondary set of analyses, exposure to FM and IM was converted to a continuous independent variable. Key Results: Forty, 333, and 374 patients were seen by FM, IM, and a combination of both services, respectively. Using average treatment on the treated as the estimand, FM care provided a shorter weight-adjusted LOS by 0.5 days (CI: -0.92- -0.04, P =0.026) compared to IM, but no difference in hospital cost (-126, CI: -906-653, P=.74). There was no difference in adjusted hazard for 30-day readmission between FM and IM (HR: 2, CI: 0.67-6.2, P =0.062). Propensity weight-adjusted multiple regression models of the complete cohort (n=747) did not show any difference in any outcomes with increased exposure to FM care. Conclusions: Understanding variation in practices and outcomes between different hospitalist models opens opportunities to improve care and decrease the length of stay.