Water solubility enhancements by two types of dissolved organic matter (DOM) extracted from a local wastewater treatment plant and by a commercial humic acid (HA) have been studied for tetrabromobisphenol A (TBBPA) using batch equilibrium technique, and the characteristics of DOM were studied with the aid of infrared and ultraviolet absorbance, elemental analysis, dialysis membranes and scanning electron microscope (SEM). The results showed that the effectiveness of DOM in enhancing solute solubility appeared to be controlled by the structure and molecular size of DOM, the ionic strength of solution and the dissociation ratio of TBBPA. Langmuir Equation could fit the isotherms of the total influent DOM and effluent DOM, and their binding coefficients (Kdoc) are 1.19 x 10(5) L x kg(-1) and 1.27 x 10(5) L x kg(-1), respectively. The interaction of TBBPA with DOM (relative molecular weight > 1000) can be explained by partition according to the linear isotherms, while the nonideal binding behavior of the total DOM was caused by DOM (relative molecular weight < 1000) which contributed about 75 % to 80% of the total water solubility enhancement effect and had higher binding coefficients to TBBPA, about 55%, than those of DOM (relative molecular weight > 1000). The capability of solubility enhancements by the influent DOM and effluent DOM was greater than that of HA in which the high molecular weight DOM controlled the effect of solubility enhancement. In addition, it was also found that the capability of solubility enhancements was affected by the ionic strength of solutions. The capability of solubility enhancements was increased when the ionic strength was low, while it was decreased at higher ionic strength due to the aggregation and flocculation of DOM.