A Petunia plant designated KLEPH18370 is disclosed. Embodiments include seeds of Petunia KLEPH18370, plants of Petunia KLEPH18370, to plant parts of Petunia KLEPH18370, and methods for producing a plant by crossing Petunia KLEPH18370 with itself or with another variety. Embodiments also relate to Petunia varieties, breeding varieties, plant parts, and cells derived from Petunia KLEPH18370, methods for producing other Petunia lines or plant parts derived from Petunia KLEPH18370, and the Petunia plants, varieties, and their parts derived from use of those methods. Embodiments further include hybrid Petunia seeds, plants, and plant parts produced by crossing Petunia KLEPH18370 with another Petunia variety or another plant type.