The flag of the Cook Islands has an aspect ratio of 1:2. It consists of a blue field (#00247D) with the Union Jack in the canton and 15 white, five-pointed stars arranged in a circle in the fly half.

The Union Jack is composed of three crosses:

1. St. George's Cross (red, #C8102E) on a white background
2. St. Andrew's Cross (white, #FFFFFF) on a blue background (#012169)
3. St. Patrick's Cross (red, #C8102E) on a white background

The 15 white stars (#FFFFFF) represent the 15 islands of the Cook Islands. Each star has an outer diameter of 1/24th the width of the flag and an inner diameter of 1/48th the width of the flag. The circle formed by the stars has a diameter of 1/2 the width of the flag, and its center is located at 3/4 of the flag's length from the hoist side and 1/2 of the flag's width from the top edge.