This paper investigates impacts of rock mass properties on dragline performance. Performances of two draglines operated in different rock formations in Tuncbilek Coal mines were analyzed using modified geological strengths index (GSI). Results showed that draglines' performance change with the rock mass properties. Based on the available data, an empirical relationship was generated to estimate dragline production capacity. The estimated excavation amount by the proposed model was found to be consistent with the excavation amount obtained from the field data.