Sn doping in an n-type transparent conducting oxide MgIn2O4 is carried out and its effect on the high temperature transport properties viz. thermopower and electrical resistivity is studied. A solid solution exists in the composition window Mg1+xIn2-2xSnxO4 for 0 < x ≤ 0.4. The band gap as well as the transport properties increases with increasing Sn concentration. The high temperature resistivity properties indicate degenerate semiconducting behavior for all the compositions. The highest figure of merit obtained is 0.12 × 10-4 K-1 for the parent compound at 600 K. © 2010.