A study of the structural and magnetic properties of carbon encapsulated iron nanowires is presented. In this work we study the influence of carbon presence in iron magnetic ordering by means of an abinitio computer simulation. We have found that for wires tightly encapsulated, i.e. large ratio of wire and nanotube radii, the influence of carbon strongly alter the Fe magnetic configuration of free standing wires, yielding AFM ordering in some cases. The energy differences between FM and AFM phases are small enough to allow their coexistence in a nanowire, which is in agreement with the experimental evidence of exchange-bias in these systems.