This work aims to offer an insight into the evolution of the CNT dispersion in preparation of a fiber-reinforced epoxy-based composite. This is done through a stepwise comparison of the dispersion qualities of multiwall carbon nanotubes (MWCNTs) in two epoxy based nanocomposite systems. The MWCNTs used in the two nanocomposites, experienced different histories in terms of the storage time while they were stored in the form of concentrated CNT/Epoxy mixtures (masterbatches). The study revealed that the older version contains large and difficult to break nanotube agglomerates. This significantly affected the rheological properties of the masterbatch in a liquid state as well as the electrical properties and glass transition temperature (Tg) of a solid nanocomposite. It is also shown that such an effect is further extended to the final fibre-reinforced composite where positioning of CNTs around the fibres seems to be controlled by the agglomeration/dispersion quality of the nanotubes in the original masterbatch.