Due to the rapid development of modern micro/nano electronic devices, polymer nanocomposites of high mechanical performance, and thermal conductivity and stability are increasingly important. We herein report a two-step process for preparation of similar to 3 nm-thick boron nitride (BN) nanosheets through noncovalent modification by a surfactant Triton X-100, which improves the compatibility of the nanosheets with the matrix as well as their dispersion. TEM micrographs demonstrated that the modified BN nanosheets (m-BN) were relatively uniformly dispersed in epoxy matrix and some were connected with each other. At 2.14 vol % of m-BN, the glass-transition temperature (T-g) and adhesive toughness of neat epoxy were improved by 17% and 355%, respectively. At 4.93 vol %, the thermal conductivity of neat epoxy was remarkably increased to 0.65 W.m(-1).k(-1), an increment of 335%. In addition, the epoxy/m-BN nanocomposites exhibited high thermal stability, which holds a potential as thermal interface materials for the next generation of electronic devices.