Experiments have been conducted to determine the viscosities of water-in-oil (W/O) emulsions in porous media. W/O emulsions were first prepared for different volume fractions of the dispersed phase and then characterized for their properties and rheological parameters including flow index and consistency constant. All prepared W/O emulsions with volume: fractions between 6.78% and 33.48% were found to behave as non-Newtonian shear-thinning fluids at fairly high viscosities. The viscosities of the emulsions were measured during emulsion flow in three types of sandpacks. A correlation of the viscosities of the W/O emulsions in porous media was developed by performing a regression on the experimentally measured data. The newly developed correlation was validated, and a sensitivity analysis was performed to examine the effects of tortuosity and emulsion quality. The emulsion quality has a dominant effect on the viscosity of the W/O emulsions and has been included in the correlation for the first time to achieve accurate predictions of the viscosities of W/O emulsions in porous media. The existing correlations for oil-in-water (O/W) emulsions provide underestimated predictions for the viscosities of W/O emulsions, whereas the droplet size distribution does not have a significant impact on the viscosity of the W/O emulsions tested in this study.