In this study, the effect of processing parameters such as roll speed and initial rolling temperature on surface irregularities of low carbon steel during multi-pass hot bar rolling process was experimentally investigated. The experiments were carried out under various roll speeds and initial rolling temperatures by using the laboratory rolling mill. The rolled bars were cut and examined by optical microscopy to check the surface quality. Finite element analyses were also conducted for given conditions to validate the experimental results. For this, an instability map developed based on the specific plastic work approach was used to determine occurrence of instability during the process. From the current study, it was found that the increase of the rolling temperature and speed is important in reducing formation of surface irregularities in the process investigated.