Onyewu's parents moved to the United States from Nigeria to attend Howard University in Washington, D.C.. Onyewu has two brothers, Uche and Nonye, and two sisters, Chi-Chi and Ogechi. Growing up in Silver Spring and later Olney, Maryland, Onyewu attended Sherwood High School where he played soccer for two years. [2] He then enrolled in a residency program in Florida, before returning to Sherwood to graduate.

Onyewu then played two years of college soccer at Clemson University, and moved to Europe in 2002, signing with FC Metz of France's Ligue 1. In 2003, he was loaned out to La Louvière in Belgium, and to Standard Liège a year later. The move to Liège was made permanent for the 2004-05 season.

Onyewu, often referred to by the nickname "Gooch," is, at 6 ft 4 in (1.93 m) and 210 pounds (95 kg), believed to be the tallest field player in team history, though two goalkeepers were taller, according to U.S. Soccer. [3]

Onyewu has been part of various U.S. youth teams, and played at the 2001 World Youth Championship. He made his first appearance for the senior national team on October 13, 2004 against Panama.

"Gooch" is remembered for losing his mark and allowing a goal to Jared Borgetti of Mexico in Azteca Stadium on March 27, 2005, only to redeem himself by dominating Borgetti in a rematch between the teams on September 3, 2005 in Columbus, Ohio. Onyewu scored his first international goal in dramatic fashion, nodding home the extra time winner in the semifinal of the 2005 CONCACAF Gold Cup against Honduras. The powerful six-foot-four defender was later named to the tournament Best XI. He has also been named to the Belgian league Best XI twice and was named Foreign Player of the Year in 2005.

Onyewu is starting for the U.S. National Team in the 2006 FIFA World Cup. If he performs well at the World Cup, it is possible that more prominent clubs in Europe would be interested in signing him.