A new and distinct cultivar of Chrysanthemum plant named `Cool Yocheryl`, characterized by its compact, upright and outwardly spreading plant habit; freely branching habit; dense and full plant habit; uniform and freely flowering habit; decorative-type inflorescences with elongated oblong to ligulate-shaped ray florets; white-colored ray florets with purple-colored apices; and natural season flowering about October 6.sup.th in the Northern Hemisphere.