On December 28, 2009, United announced the signing of Curt Onalfo, the former Kansas City Wizards coach who had previously been fired following a 6–0 defeat to Dallas in August 2009.

Although the team had an abysmal regular season showing, they excelled in U.S. Open Cup competition, making a run to the semifinals, before bowing out against Columbus.

To prepare for the 2010 season, United participated in the Carolina Challenge Cup, hosted friendlies at the IMG Academy in Florida, as well as traveled to Mexico to take on Santos Laguna.

[1] United would drop three more consecutive season games in April, which led the club off to a 0–5–0 start, their worst in franchise history.

Onalfo received sharp criticism from fans and the media alike, but expressed hope and optimism for a turnaround during the season.

In the wrath of a horrendous start to the season, United had scheduled a friendly against the Italian Serie A giants, A.C. Milan.

The confidence from the Milan-match benefited United in their next two matches; a May 29 come-from-behind victory hosting Chivas USA and a U.S. Open Cup qualifier against Real Salt Lake on June 2.

June began with a pair of matches against Real Salt Lake; one for the U.S. Open Cup, and another for the regular season; both at RFK Stadium.

The Open Cup match was played on June 2, with United beating Real Salt Lake 2–1, thanks an Andy Najar-goal after extra time.

Despite their lack of victory during the month, they continued to find success in the U.S. Open Cup in which United won their quarterfinal-match on July 21 against USL Second Division's Harrisburg City, 2–0.

United ended a stony note when traveling to Rio Tinto on July 31 to take on the second-place Real Salt Lake.

Goals from RSL's panel of stars including Robbie Findley and Alvaro Saborio saw United crash to a 3–0 defeat to end the month.

Under Olsen's leadership, United earned their first win in over two months in a 2–0 victory over local rivals, the Philadelphia Union on August 22.

In hope to salvage their abysmal season, United played a full strength lineup in the U.S. Open Cup semifinals against Eastern Conference-rival Columbus Crew.

Thanks to Hernández's 13th-minute penalty kick, United took a 1–0 lead over Columbus for nearly the entire match; however, in the last minute of play, an own goal by Mark Burch forced the game to go into overtime, where a penalty kick from the Crew's captain, Guillermo Barros Schelotto, ultimately led United to bow out of the tournament.

The loss ultimately has made it incredibly difficult and arduous to qualify for the 2011–12 edition of the CONCACAF Champions League.

This started out with the signing of Guyanese international, JP Rodrigues on loan from Miami FC of the USSF D2 Pro League.

D.C. United lost its 19th game 2–0 to San Jose, marking their tenth loss at home, a team worst, as well as the 16th time this season they were shut out, an MLS record.

On November 3, midfielder Andy Najar won the Rookie of the Year Award,[9] ahead of fellow rivals New York's defender, Tim Ream and Philadelphia Union's striker, Danny Mwanga.

Two weeks later, on November 15, the United and striker Danny Allsopp mutually agreed to terminate his contract valued at $217,000 guaranteed pay from the club.

Note: Flags indicate national team as defined under FIFA eligibility rules; some limited exceptions apply.

Win Tie Loss D.C. United's fifteenth season in Major League Soccer began on March 27 and ended on October 23.