The flag was adopted by the Lei nº 1.050, of 24 July 1922, and was amended by the Lei ordinária no 5.507, of 17 November 2005.

Its drawing consists of a rectangle with the proportions 7:3, divided in thirteen interspersed green and yellow stripes with the same length.

In the upper right corner there is a dark blue canton with the length equal to five stripes with a white star in the middle.

The colors used on the flag (green, yellow, blue and white), don't have an official shading level.

However, the manual of visual identity of the government of the Piauí state specifies the following colors:[1] The main colors of the flag are the same as in the Flag of Brazil and are one representation of the integration of the state with Brazil.