A new and distinct cultivar of Chrysanthemum plant named `Yokilleen`, characterized by its upright, outwardly spreading and mounded plant habit; strong and freely branching growth habit; dark green-colored foliage; uniform flowering response and habit; early and freely flowering habit; decorative-type inflorescences with quilled-shaped and bright green-colored ray florets; and good postproduction longevity with plants maintaining good substance and color for about three weeks in an interior environment.