We report a theoretical investigation on a B 12 cluster, which can exhibit a through ring umbrella inversion. Our calculations show that a part of the molecule consisting of a three membered boron ring can invert through the rest, viz., a nine membered boron ring. Using a simple model we calculate the double well potential for the motion. The barrier for inversion is found to be 4.31kcal/mol. The vibrational levels and tunneling splitting are calculated using this potential. We find that the vibrational excitation to the v=17 level will cause large amplitude “inversion oscillation” of the molecule. After including the tunneling effect, inversion rate at 298K is calculated using transition state theory and is found to be 1.17×10 10 /s.