Hospitalists, or specialists of hospital medicine, have long been practicing in Canada and Europe. However, it was not until the mid-1990s, when hospitals in the U.S. started widespread adoption of hospitalists. Since then, the number of hospitalists has grown exponentially in the U.S. from a few hundred to over 50,000 in 2016. Prior studies on hospitalists have well documented benefits hospitals gain from adopting this innovative staffing strategy. However, there is a dearth of research documenting predictors of hospitals’ adoption of hospitalists. To fill this gap, this longitudinal study (2003–2015) purposes to determine organizational and market characteristics of U.S. hospitals that utilize hospitalists. Our findings indicate that private not-for-profit, system affiliated, teaching, and urban hospitals, and those located in higher per capita income markets have a higher probability of utilizing hospitalists. Additionally, large or medium, profitable hospitals, and those that treat sicker patients have a higher probability of adoption. Finally, hospitals with a high proportion of Medicaid patients have a lower probability of utilizing hospitalists. Our results suggest that hospitals with greater slack resources and those located in munificent counties are more likely to use hospitalists, while their under-resourced counterparts may experience more barriers in adopting this innovative staffing strategy.