The application of nanoparticles as a catalyst in porous media has recently been increased and is generally relevant to applications that include in situ heavy oil upgrading and removal of reactive and non-reactive pollutants in groundwater. The objective of this paper is investigation of the effects of reactive nano-catalysts on viscous fingering instability. In order to understand the behaviour of frontal instabilities during transport of reactive nanoparticles, the basic equations of conservation of mass and momentum are linearized and solved numerically. The analysis reveals that increasing the reaction rate promotes the viscous fingering instability around an interface delivering nano-catalysts, while increasing the nano-catalysts deposition rate usually stabilizes the displacement front. It is also shown that accumulation of nano-catalysts behind the front can destabilize the reactive front. The effects of the interface sharpness, nanoparticles diffusion coefficient, permeability of porous media, and viscosity ratios of different phases are also discussed. (c) 2012 Elsevier Ltd. All rights reserved.