A new and distinct Threadleaf Coreopsis plant, Coreopsis verticillata plant named ‘;Sassy Saffron’;, with narrowly-linear, deeply-dissected, typically 3 to 6-lobed foliage of bright-green, numerous flowers of rich lemon-yellow ray florets with deep maroon center over a prolonged flowering season from mid-June until late summer. The new plant is useful for landscaping as a specimen plant, en masse, in containers and as a cut flower.