Experiments were conducted to analyze the viscous fingering instability that develops during the displacement of oil-in-water (O/W) emulsions. For this purpose, a horizontal rectilinear Hele-Shaw cell, which is an analogue for a homogeneous porous media, was used. Different emulsion solutions were prepared by dispersing different volume fractions of mineral oil in water using non-ionic surfactants. These emulsions were characterized systematically by examining their droplets size distribution and shear viscosity. Flow displacement experiments involved displacing the O/W emulsions by injecting water at different rates. The developments of the instability were characterized qualitatively by identifying the main mechanisms of finger development and growth. These results and the correlations between the properties of the fluids and the flow patterns were used to examine the flow dynamics and its effects on the viscous fingering instability. It was found that the development of the flow instability can be correlated with the rheological behaviour, which in turn depends on the emulsions' concentration and their internal microstructure.