Ionic liquids are widely under research due to their potential properties as solvents. The prediction of their physicochemical properties is an important strategy to achieve a better knowledge for further applications. The present work applies a group contribution method to estimate the viscosity at different temperatures of a new generation of ionic liquids, magnetic ionic liquids (MILs), which are comprised by anions containing transition metal complexes. These new substances have received a high interest due to their response at the presence of a magnetic field. In this study the magnetic ionic liquids are based on the phosphonium cation [P-66614](+) with different chain lengths and on the magnetic anions: [GdCl6](3-), [MnCl4](2-), [FeCl4](-) and [CoCl4](2-). The database covers a wide range of temperature, 293.15-373.15 K, and viscosity 44-123 500 cP. The modelling estimations show a good agreement with the experimental results, presenting a mean percentage deviation of 7.64%. These results confirm the interest of this model for the estimation of viscosity and the influence of the temperature, which can be extended for a large variety of group combinations in magnetic ionic liquids leading to different applications. (C) 2013 Elsevier B.V. All rights reserved.