Plant derived compounds have been reported for their anticancer as well as antioxidant potential. Thymoquinone, the bioactive principle of Nigella sativa seeds possess a wide array of beneficial as well as pharmacological effects. The present study was aimed to evaluate the effect of thymoquinone on the levels of tumor markers and proinflammatory cytokines, NF-κB and nitric oxide in experimental groups of rats. A single dose of 7, 12-Dimethylbenz (α) anthracene (DMBA) (20 mg/kg/rat) diluted in olive oil was given orally to induce breast cancer. Thymoquinone (25 mg/kg body weight) was orally administered to DMBA Induced breast cancer rats. All animals were sacrificed after 13 weeks of experimentation. The important diagnostic biochemical indices of breast cancer (tumor markers) such as Alpha-fetoprotein (AFP), Carcinoembryonic Antigen (CEA) and Cancer Antigen 15-3 (CA 15-3), Serum Total Sialic Acid (TSA) and Lipid-bound Sialic Acid (LSA) were assayed in the serum. The anti-inflammatory potential of thymoquinone was determined by measuring the levels of proinflammatory cytokines such as Tissue Necrosis Factor (TNF-α), Interleukin-1β (IL-1β), Interleukin-6 (IL-6) in the liver and kidney tissues. There was an observed decrease in the levels of tumor markers and declined proinflammatory cytokines level in the rats treated with thymoquinone. The results of the present study indicate that thymoquinone possess anti-inflammatory potential.