Congress is the legislative branch of the government of the United States of Mexico. As established by the Constitution of 1819 at the Mexico City Convention, the Congress consists of two houses: the upper house, called the Senate, represents the states, while the lower house, called the Assembly, represents the people. Although the Congress is normally chosen by regularly scheduled elections, the President, who is the head of the executive branch of the government, has the power to call new elections when he feels them necessary. The President also has the power to veto laws passed by the Congress, although the Congress can override the President's veto by a two-thirds vote of each house.

Although Sobel does not say so, it seems certain that the Congress was named after the Continental Congress by Andrew Jackson.