The flag of São Tomé and Príncipe has an aspect ratio of 1:2. It consists of three horizontal stripes and a red isosceles triangle. The top stripe is green (Pantone 347), the middle stripe is yellow (Pantone 116), and the bottom stripe is green (Pantone 347) again. The red triangle (Pantone 485) is based on the hoist side, with its height equal to the flag's width and its base equal to half the flag's length.

The yellow stripe is narrower than the green ones, with a proportion of 1:3:1. In the center of the yellow stripe, there are two black stars (Pantone Black) with five points each, representing the two main islands of the country. The stars are placed horizontally, with one point of each star pointing upwards.