Scrub typhus is an acute febrile disease caused by the pathogenic bacterium Orientia tsutsugamushi, belonging to the Rickettsiaceae family. The shotgun proteomic analysis was performed using the sera of scrub typhus patients to identify the proteins having their origin in O. tsutsugamushi. Three different databases approaches were used for the identification of the proteomes. We identified the RsmD, an RNA methyltransferase as the commonly detected protein from all three approaches. This protein was not detected in the sera of healthy negative controls. We believe that this protein is a potential biomarker of Orientia tsutsugamushi present in the sera of scrub typhus patients.