Heat dissipation is a critical issue in many areas such as the high-performance electronic devices. The present work gives a detailed investigation regarding a simple and efficient surface modification method, which can remarkably improve the thermal conductivity of the isotropically thermally conductive adhesives (TCAs). Herein we demonstrate that the thermal conductivity of TCAs based on micron-sized silver fillers can be improved to near eightfold merely through simple surface chemistry treatment of the fillers, without changing the conventional epoxy resin (adhesive) processing conditions. Experimental results show that the thermal conductivity of a TCA sample with iodine modified silver fillers (85wt%, size 1-2μm, near-spherical particles) achieved 13.5Wm -1 K -1 when cured at 150°C. Compared to the unmodified silver-based TCAs, only 1.7Wm -1 K -1 was achieved when cured in the same condition. This work suggests that through modulating the filler interface of a TCA, the thermal conductivity of a TCA can be drastically improved. These TCAs with superior isotropic thermal conductivity may find many heat dissipation applications e.g. surface mounted devices (SMDs) and high power (printed circuit) motherboards.