Abstract The aim of this study was to investigate the effect of preimpregnation of thermally modified wood (TMW) with paraffin wax emulsion (WE), which was loaded with disodium octoborate tetrahydrate (DOT). The improvements of physical, mechanical, and biological properties of WE DOT -TMW was in focus. The thermal modification (TM) was conducted at 220°C for 4 h. The equilibrium moisture content (EMC), water absorption, volumetric swelling, bending strength, mold and termite resistance of WE DOT -TMW were determined. The boron leaching data were also determined, while the borate was analyzed by Inductively coupled plasma atomic emission spectroscopy (ICP-AES), followed by the model fitting according to a pseudo-second order differential model. The results indicate that WE DOT improved water repellency, dimensional stability, bending strength as well as the mold and termite resistance of WE DOT -TMW. The boron leaching of WE DOT -TMW was reduced compared with DOT-TMW due to the hydrophobic effect of WE. The pseudo-second order differential model describes accurately the boron leaching process from WE DOT -TMW.