A novel active TE-TM mode converter in a poled electrooptic polymer waveguide is demonstrated, The mode converter utilizes a 45 degrees-off poling configuration, which can be obtained by arranging upper- and lower-stripe poling electrodes with a proper lateral displacement, The mode-conversion properties and electrooptic effect are demonstrated by using a vector-beam propagation method in a buried channel-type waveguide, Applications to integrated polymer-waveguide devices are also suggested.