A method of controlling an image projection system that includes a plurality of projectors including a first projector and a second projector having a lens shift function, and that includes an imaging device, includes: projecting, by the first projector, a first pattern having a first color tone; projecting, by the second projector, a second pattern having a second color tone; generating, by the imaging device, a captured image obtained by capturing a composite image including the first and second pattern; determining, by the first projector, whether an area of an overlapping portion of the second pattern in the captured image is equal to or larger than a predetermined ratio; and causing, by the first projector, the second projector to perform lens shift by the lens shift function of the second projector such that the second pattern overlaps the first pattern, when the area is less than the predetermined ratio.