After his junior season, Wolff left college and signed with Major League Soccer. MLS assigned Wolff to the Chicago Fire. He set the MLS rookie scoring record by scoring eight goals, doing so in just 14 games with only four starts. Wolff played the following four seasons for the Fire, scoring 24 goals, but suffered through multiple injuries. Before the 2003 MLS Superdraft, the Fire traded Wolff, in a cost-cutting move, to the Kansas City Wizards in exchange for the third overall pick, which the Fire used to select Nate Jaqua. Wolff missed most of the 2003 season due to injuries. He rebounded in 2004 by scoring ten goals and seven assists during the season. Wolff scored his first career playoff goal on a penalty kick during the MLS Cup 2004. He scored ten goals and ten assists in 2005. In September 2006, Wolff had a try out with English Championship club Derby County. The team was pleased enough with his performance to offer MLS a $500,000 transfer fee. However, British immigration officials denied Wolff a work permit based on the fact he had failed to play the required 75% of the U.S. national team's games in the previous two years. From England, Wolff traveled to Germany for a try out with 2. Fußball-Bundesliga club 1860 Munich. On December 6, 2006, 1860 Munich signed Wolff to a contract through the 2007–2008 season. Munich paid MLS a $191,000 transfer fee. Wolff joined the team during its January 2007 mid-winter training camp but was waived at the end of the 2008 season. Wolff signed with the Kansas City Wizards on June 30, 2008. At the end of the 2010 MLS season, after two and a half seasons back in Kansas City, Wolff's contract option was declined by the club. On December 15, 2010, Wolff was selected by D.C. United in Stage 2 of the 2010 MLS Re-Entry Draft and immediately signed a one-year contract with a club option for 2012. Wolff announced his retirement on November 28, 2012, and became a full-time assistant coach with D.C. United. He joined the Columbus Crew in November 2013, and remained assistant coach until 2018. In 2018, Wolff joined the staff of the United States Men's National Team under Gregg Berhalter. On July 23, 2019, Wolff was named the first coach for MLS team Austin FC, which will begin play in 2021.
International
Wolff has scored nine goals in fifty-two caps since his debut against Jamaica on September 8, 1999. He also starred for the US in the 2000 Summer Olympics, scoring two goals and helping the team to a fourth-place finish. As with his club teams, however, Wolff has had trouble securing a definite spot because of continual injury problems. He did play for the United States in the 2002 World Cup, assisting on the opening goal in the second-round win against Mexico. On May 2, 2006, Wolff was named to the US roster for the FIFA World Cup in Germany. Wolff played his last national team match versus Spain at Estadio El Sardinero on June 4, 2008.
