The flag of Guinea-Bissau has an aspect ratio of 1:2 and consists of three vertical stripes and a red star on a black triangle. The stripes are, from left to right, yellow (Pantone 116 C), green (Pantone 347 C), and red (Pantone 186 C). The black triangle (Pantone Black C) is located on the hoist side, with its base along the entire height of the flag and its apex touching the center of the flag. The red star (Pantone 186 C) is centered within the black triangle.

The width of each stripe is equal, taking up one-third of the flag's total width. The height of the black triangle is equal to the flag's height, while the length of the triangle's base is half the flag's height. The red star is inscribed in an invisible circle with a diameter equal to one-fifth of the flag's height.