Reyes was born in Canutillo, Texas. Reyes served in the United States Army and he worked for the U.S. Border Patrol. In 1993, serving as the Chief Patrol Agent of the El Paso Border Patrol Sector, Reyes lead the Border Patrol to position agents on the border to intercept illegal immigrants. Crime went down as a result of his move. Reyes resigned from the INS and began to run for Congress against Congressman Ron Coleman but Coleman retired. Reyes was elected to the House of Represenatives as a Democrat in 1996. Reyes is the leader of the Hispanic Caucus and in 2002, he considered running for the United States Senate but decided against such a move. In 2005, because of the death of his mother, he missed 94 votes in the House, the ninth most of any member. On December 28, 2005 an El Paso substitute teacher, Jorge Artalejo, filed an application to run against Reyes in the March 7, 2006 Democratic primary 1 . Silvestre Reyes' brother, Jesus "Chuy" Reyes, is the manager and a board member of the El Paso Water Improvement District No. 1. Silvestre Reyes' sister-in-law, Martha "Marty" Reyes is running for state representative against the incumbent "Craddick Democrat", Norma Chavez, in the 2006 primary.

Reyes has been a key player in the 109th Congress because of his Immigration and Border Patrol experience. He was instrumental in leading the opposition to the house immigration proposal known as the "Sensenbrenner bill" largely criticized as "mean spirited" and "anti-immigrant". Democratic Leader Nancy Pelosi selected Reyes to present and lead the debate on a Democratic substitute to replace the Sensenbrenner legislation. It was voted down on a party line vote.

As a senior member of both the Armed Services and Select Intelligence Committees Congressman Reyes is a key member of Congress on Defense and military issues. His leadership is credited with the recent success of Fort Bliss and White Sands military bases in the most recent Base Realignment and Closure (BRAC) decisions by the Department of Defense.