Nanofiller-modified polymer matrix composites (PMCs) have been much studied as multi-functional materials. To date, however, work in this area has overwhelmingly focused on single-filler composites such as, for example, carbon nanotube (CNT)-modified polymers. Furthermore, work on multi-filler systems has focused on fillers with complementary attributes (e.g. achieving higher electrical conductivity in CNT + graphene composites than can be achieved via modification with either CNTs or graphene alone). As an alternative, we herein propose a new approach: dissimilar functional fillers selected for synergistic interactions. That is, we seek to identify combinations of nanofillers that interact with each other in order to give rise to unique multi-functional capabilities not achievable by either filler individually. To that end, we present preliminary work on CNT + carbon-coated iron nanoparticle (CCFeNP)-modified PMCs. CNTs and CCFeNPs were selected due to their complementary geometry (i.e. high aspect ratio CNTs and spherical CCFeNPs, which gives rise to higher electrical conductivity) and their potential for synergistic electro-magnetic interactions in a percolated network. These preliminary results report on the electro-magnetic properties of CNT + CCFeNP/epoxy composites including AC and DC conductivity and magnetic permeability as a function of varying CNT and CCFeNP concentration. It is hoped that further exploration into synergistic functional filler combinations will lead to new multi-functional capabilities in the future.