Oxidative stress plays a key role in the pathogenesis of several diseases, including neurodegenerative diseases. Recent studies have reported that mitochondrial dysfunction is a leading cause of the overproduction of reactive oxygen species and oxidative stress. Mitochondrial changes play an important role in preventing oxidative stress. However, there is a lack of experimental evidence supporting this hypothesis. Thymus quinquecostatus CELAK (TQC) extract is a plant from China belonging to the thymus species, which can mediate the inflammatory response and prevent cell damage through its antioxidant activities. This study examines whether TQC can scavenge excess ROS originating from the mitochondria in RAW 264.7 macrophages. We used lipopolysaccharide (LPS) to induce inflammation and oxidative stress in RAW 264.7 macrophages and performed an immunocytochemistry dot blot of 8-hydroxy-2′-deoxyguanosine (8-OHdG) and real-time PCR to analyze the expression levels of genes involved in mitochondrial biogenesis and oxidative metabolism. TQC was found to significantly reduce the intensity of immunostained MitoSOX and 8-OHdG levels in the total genomic DNA within the mitochondria in RAW 264.7 macrophages. The HO-1 and Nrf2 mRNA levels were also significantly increased in the TQC groups. Therefore, we verified that TQC improves mitochondrial function and attenuates oxidative stress induced by LPS. Our results can provide reference for the effect of TQC to develop new therapeutic strategies for various diseases.