© 2019 The Chemical Society of Japan. Transient circular dichroism (TR-CD) spectra of (P)- and (M)-hexahelicenes (HHs) in the excited triplet state, (P)- and (M)- 3 HH ∗ , and their growth and decay behaviors in the μs time domains were recorded for the first time in toluene at room temperature, using an improved Kliger's method. The TR-CD spectra of (P)- and (M)- 3 HH ∗ obtained were mirror-imaged, exhibiting strong positive and negative Cotton effect, respectively, of δϵ| = 55M -1 cm -1 for the lowest-energy band at 660nm and additional sign-alternating less intense peaks in the higher energy region, the major features of which were well reproduced by the TD-DFT calculations at the UCAM-B3LYP/ 6-31G(d,p) level.