The viscosity of the binary and ternary systems of tragacanth (T), guar (G) and methylcellulose (MC) was obtained by means of a rotational viscometer in the range of concentration from 1 to 10 g/L at 25, 35, 45 and 55C. The modeling was based on polymer concentration, temperature and shear rate. The viscometric parameters, flow and consistency indices were evaluated as a function of the cited variables, obtaining the corresponding correlations. Interactions between polymers are hypothesized because of its structure and molecular weight. An interaction parameterΔηijwas calculated for modeling. As expected, in all the cases, the apparent viscosity decreases with temperature and it was introduced in the proposed models for T–G and G–MC systems. Synergistic effects were found for T–G in all the cases and G–MC when G concentration was higher than MC concentration. These results could suggest that interactions between MC and G molecules are generated.