Conventional high-performance thermosets are gaining increased interest due to their advantageous properties, i.e. low coefficient of thermal expansion, high Tg and high chemical resistance. For electrical applications, i.e. Printed Circuit Boards, high thermal conductivity and flame retardancy are additional requirements, which thermosets do not meet. In literature, the addition of ceramic fillers with high intrinsic thermal conductivity, i.e. Boron Nitride (BN) or Aluminium Nitride, to thermoset matrices are extensively studied. This way, the heat dissipation within the bulk volume can be managed by the formation of a micro-structured network. However, the simultaneous combination of thermal conductivity and flame retardancy is an approach which is not studied yet. Therefore, intrinsic thermally conductive fillers, i.e. Boehmite and hexagonal BN are investigated towards their potential to enhance the thermal and flame retardant properties in Epoxy Novolac matrices. The focus of this scientific work is to correlate the resulting thermal properties with the fillers’ particle size, morphology, content, dispersion and orientation which is investigated with microscopic methods (SEM, TEM). Both filler types are studied systematically as monomodal and bimodal filler distributions and finally as hybrid formulations. The thermal properties of the resulting composites are determined via TGA, DMA (Tg), TMA (z-CTE) and heat flow meter. The effect on flame retardancy is examined with Cone Calorimetry and UL-94. The results show that the thermal conductivity is strongly dependent on filler content particle size and its morphology. With increasing filler content and the higher the filler’s aspect ratio, the more pronounced is the effect on thermal conductivity and flame retardancy. Furthermore, the variation in the relative composition of the bimodal filler distributions demonstrated the potential to design the conducting micro-structured network in a smart way.