Recently, research on the application of magnetorheological (MR) fluid in mechanical engineering has been widely expanded, while the performance of MR fluid in tribology has also been investigated. In this study, a modification of MR fluid, which is modified by adding certain additives, is attempted to improve tribological performance. After modification, wear and friction are measured by four-ball wear tester and linear-oscillation (SRV) tester under no magnetic fields. Subsequently, the oxidation induction time (OIT) is evaluated by pressure differential scanning calorimetry (PDSC). Then, to observe the tribological performance under magnetic fields, pin-on-disk test is conducted to confirm the effects of the commercial MR fluid and modified MR fluid on friction and wear in different operating and magnetic conditions. Also, the modification effects on surface roughness are investigated by using a profilometer. Moreover, the microscopic changes of surfaces and MR particles are investigated by using scanning electron microscopy (SEM).