Today, herbs are used as adjuncts to reduce the toxicity of chemotherapy drugs. Here, Zataria-Multiflora Essential Oil (ZEO) was concomitantly employed with doxorubicin, as an anti-cancer drug, to reduce the doxorubicin dosage. The growth inhibition was determined using MTT assay in treated cells. The morphological alteration was observed by fluorescent staining. To verify and compare the apoptosis, AnnexinV-PI flowcytometry and DNA fragmentation assay were performed, and the influence of the compounds on ROS generation was assessed. Changes in MMP and protein expression were analyzed by flowcytometry and western blot, respectively. The results showed that ZEO can act as an amplifier to sensitize PC3 prostate cancer cells to undergo ROS generation and apoptosis. This amplification can heighten the doxorubicin efficacy in lower doses. Consequently, our results indicated that doxorubicin-ZEO combinatory treatment of PC3 cells can reduce the nonspecific toxicity of doxorubicin and can be considered as a candidate in combinatory therapy.Copyright © 2020 Elsevier Ltd. All rights reserved.