Effects of a radial magnetic perturbation (MP) on electron cyclotron (EC) driven fast electrons are investigated in the Low Aspect ratio Torus Experiment (LATE) device. When a weak MP is applied to plasmas maintained solely by EC heating and current drive, plasma current and electron density increase, whereas energetic trapped electrons located outside the last closed flux surface (LCFS) on the low field side (LFS) decrease. The effect of MPs on energetic trapped electrons has an important role in improving EC-driven plasma discharges © 2012 The Japan Society of Plasma Science and Nuclear Fusion Research.