It is a muscle of facial expression, which draws the angle of the mouth superiorly and posteriorly to allow one to smile.

Bifid zygomaticus major muscle is a notable variant, and may cause cheek dimples.

The zygomaticus major muscle originates from the superior margin of the lateral surface of the temporal process of zygomatic bone,[1] just anterior to the zygomaticotemporal suture.

[2] The zygomaticus major muscle may occur in a bifid form, with two fascicles that are partially or completely separate from each other but adjacent.

[1][3] It is thought that cheek dimples are caused by bifid zygomaticus major muscle.