The desire of tailoring thermal conductivity of composites, along with its already known superior mechanical properties, is gaining more importance in the quest of reducing life cycle cost and improving system reliability of environmental control systems, aircrafts, and spacecrafts. Future aircrafts are expected to be designed with distributed power devices (such as, rechargeable batteries, capacitors, heat exchangers, etc.) than one central unit. Thus, structural systems will require adequate thermal efficiency to efficiently manage the heat generated by these devices. In almost all cases these heat generating devices are attached to the structural members by adhesive joints, thus suitable materials system to enable through-thickness thermal conductivity in adhesive joints. In addition, the transverse thermal conductivity in composite materials is equally important in this respect. The materials interfaces in heterogeneous materials systems play a big role in dictating the thermal as well as the mechanical properties. We have demonstrated, through unique processing schemes and simulation, the importance of materials interface and its morphology, at different scale levels (nano to micron scale), in tailoring of the thermo-mechanical properties of composites. A few materials systems will be discussed.