This study was designed to compare the inhibitory effects of thymoquinone (TQ) and curcumin (CMN) on the biological changes associating asthma. TQ appeared to exhibit greater inhibitory effects on the aggregation of inflammatory cells in bronchoalveolar lavage (BAL) fluid and in lung tissues. We also measured the effects of the two agents on serum IgE and the changes in the mRNA levels of inducible nitric oxide synthase (iNOS), tumor necrosis factor-α (TNF-α) and transforming growth factor-β1 (TGF-β1). Serum IgE was significantly decreased by TQ and CMN with TQ being more potent. Also, TQ showed superior inhibitory effects on iNOS and TGF-β1. Meanwhile, CMN was more potent in inhibiting mRNA expression of TNF-α. These results suggest that TQ is more potent in inhibiting the inflammatory changes associating asthma. On the other hand, CMN was a less potent inhibitor of all measured parameters, despite its superior inhibitory effect on TNF-α mRNA levels.