This research describes an investigation of the interfacial phases formed between aluminum (Al) and carbon nanotubes (CNT) which properties depend on the processing temperature (below, slightly above and over the melting point of Al). Al CNT compacts were prepared by spark plasma sintering followed by heat treatment in order to observe the interface phases. The microstructures of both the as-sintered and heat-treated materials have been observed by optical, scanning and transmission electron microscopies. The amorphous Al oxide observed at the boundaries in the as-sintered material is transformed to crystalline Al oxide after the heat treatment. In addition, some of the CNTs decomposed and reacted with the Al, resulting in the formation of Al carbide which shows different size distributions depending on the heat treatment temperature. According to the results, it is possible to control the phase formed at the Al CNT interface by controlling the process temperature and those controlled interfaces will be playing important role to the properties in a bulk materials. (C) 2013 Elsevier B.V. All rights reserved.