A projection image adjustment system includes: a pattern generator decomposes a projection test pattern into binary test patterns individually corresponding to first attributes to be expressed in a binary manner; a projection display apparatus projects a projection image and the binary test patterns; a pattern combining unit generates binary captured images by individually binarizing captured images generated by capturing the projected binary test patterns and combines the binary captured images into a combined captured image; and a calculator transforms the projection image by using a relationship between positions of feature points in the combined captured image and positions of the feature points in the projection test pattern. The projection test pattern includes divided regions, each of the regions includes a second attribute to be expressed by a combination of the first attributes, and each of the feature points is a point shared three or more adjacent regions among the regions.