The Senate unanimously approved the deal Thursday in its last session of the year.
The text of the measure voted on by upper house said the pact will open up these markets to Mexican products while "promoting the Mexican economy's integration with the Central American region and helping boost competitiveness."
The accord, signed on Nov. 22 in El Salvador, would eliminate most tariffs between Mexico and the Central American nations in 2012.
Under negotiation since 2008, the agreement seeks to facilitate and increase trade "under a single set of rules and regulations," strengthen productive chains and provide certainty to investors, the text read.
It also establishes rules for protecting intellectual property rights and guidelines for bilateral, regional and bilateral cooperation.
According to Mexican government figures, Central American imports amount to nearly $50 billion annually and Mexico accounts for roughly 8 percent of that total.
Trade between Mexico and Central America amounted to $6.55 billion in 2010.
Also Thursday, the Mexican Senate ratified a controversial trade deal with Peru after ignoring the recommendations of its own Trade and Industrial Development Committee, which said the accord lacked a clear legal framework and will hurt Mexico's agricultural sector.
Mexico's agriculture and fishing sectors had lobbied the Senate not to ratify the treaty, saying it would adversely affect domestic growers of "sensitive products" such as chili peppers, beans, plantains, onions, avocados, potatoes, mangos and grapes.
Seven of the 12 members of the Trade and Industrial Development Committee found enough merit in that argument to recommend against approving the accord.
But the governing conservative PAN managed to get the pact ratified thanks to support from the PVEM, a minor party.
The "no" votes came from the leftist PRD and the main opposition Institutional Revolutionary Party, or PRI.