Carbon nanotubes (CNTs) and trace contaminants often co-occur in natural waters and wastewaters, and they may become the precursors of disinfection byproducts (DBPs). However, the effects of CNTs on the formation of DBPs during chlorination of co-existed organic pollutants are unknown. This study compared the effects of three types of CNTs on the formation of DBPs during chlorination of bisphenol A (BPA). The results showed that, compared with the single system of BPA, CNTs significantly decreased the initial rate (R-i) and the second-order rate constant (k) of trihalomethanes (THMs) formation in the binary systems of CNTs and BPA. For example, R-i for the binary system (38.7-49.6 mu g/(L.h)) was much lower than that for the single system of BPA (63.1 mu g/(L.h)). Furthermore, the suppression effects depended not only on the type but also on the concentration of CNTs: the suppression of R-i and k by CNTs followed the order of pristine CNTs > hydroxyl CNTs > carboxylic CNTs, and increased with rising concentration of CNTs. The adsorption experiments and density functional theory (DFT) calculation further revealed that higher adsorption and stronger binding of BPA to CNTs resulted in greater suppression degree of R-i and k by CNTs.