The significant effect of the addition of very small proportions of nanofibres and nano-particulates on the physical and mechanical properties of solid materials has been long observed and described. The effect of addition of electrospun fibres on the physical properties of liquid has not been so widely examined. In this paper, the effect of the addition of polyvinyl alcohol (PVOH), and zein nanofibers in sunflower (Helianthus annuus) oil on its viscosity was observed and quantified. For a given amount of material, a trend of increasing effectiveness was found as fibre diameter reduced. The addition of 0.01% (by mass) of fibre increased the kinematic viscosity of oil samples by 15%. The presence of fibre in oil was confirmed by light microscopy whilst the size of the fibres was measured by the analysis of scanning electron microscope images (SEM). This phenomenon of a low concentration of nanofibers significantly increasing viscosity may find practical applications as a foodstuff thickener.