The Sounders opened the regular season with a 2–0 victory over expansion side Philadelphia Union on March 25, 2010, at Qwest Field in Seattle.

[2][3] In winning the U.S. Open Cup tournament, Sounders FC qualified for the preliminary round of the 2010–11 CONCACAF Champions League.

In 2009 Sounders FC became the second MLS expansion team in league history (Chicago again was first) to qualify for the playoffs in their first season.

[5][6] Sounders FC's inaugural season came to an end in the 2009 MLS Cup Playoffs when they lost in the conference semifinals to the Houston Dynamo with a 1–0 aggregate score in a two-legged series.

[17] On March 11, the inaugural Seattle Sounders FC Community Shield preseason match was played against the Portland Timbers continuing the Portland-Seattle rivalry.

[19][20] Joe Roth, Sounders FC Majority Owner stated, "Being selected to participate in the first match of the season is a testament to the passion and energy of our fans.

[22] On April 9, Seattle played their first road match of the season, facing the defending MLS Cup champion, Real Salt Lake, in Sandy, Utah.

The game appeared to be ending a scoreless tie until late substitute Michael Fucito scored his first career goal in 92nd minute of the match off a throw in from Brad Evans.

This was Seattle's worst ever defeat at home and it was played in front of a team record attendance for a regular season match of 36,273 fans.

[30] The day after the lopsided defeat to Los Angeles, Sounders FC owner Adrian Hanauer announced a refund for all 32,000 season ticket holders for the embarrassment and indicated that changes were in the works for the club.

[37] After the World Cup break, the Sounders FC went to play the Philadelphia Union at the new PPL Park in front of a crowd of 18,755 during a humid day.

[38] The Sounders FC began their U.S. Open Cup defense in a rematch against rivals to the south Portland Timbers at a sold-out PGE Park.

[39] The Sounders FC went down to Carson, California on July 4 to play the Los Angeles Galaxy, who they previously lost to 4–0 at home in May.

[44] The team returned to action on July 25 at home against the Colorado Rapids in a game nationally televised on Fox Soccer Channel.

Steve Zakuani got the Sounders on the board in the eighth minute, but Colorado's Omar Cummings answered thirty seconds later, technically in the ninth.

[45] The Sounders continued their winning streak at home with a 1–0 victory against Isidro Metapán in the CONCACAF Champions League preliminary round.

Newly signed midfielder Álvaro Fernández headed a pass from James Riley in the 74th minute, which equalized the score and let the team advance 2–1 on aggregate.

In a rough first half that included 19 combined fouls and three yellow cards, Chicago struck first when Jeff Parke was deemed to have handled the ball in his own penalty area.

[56] Sounders owners chartered an airplane to take the team to Estadio Ricardo Saprissa Aymá in San José, Costa Rica to face C.D.

Leo Gonzalez was sent off in the 38th minute and the home side capitalized on the man advantage to win the match 2–0[57] The team flew directly from San José to face the Columbus Crew on September 18.

Kasey Keller was tested repeatedly but kept a clean sheet and Blase Nkufo scored in the 88th minute to give the Sounders the 0–1 win.

They would need to win against incoming Toronto FC, whom were looking for one of the final seeds in the playoffs, and then travel out to Kansas City to take on the Wizards, another team longing for postseason action.

[62] Finishing 6th overall, Seattle won the fourth-seed in the Western Conference championship in the MLS Cup playoffs going against Supporters' Shield-winners, Los Angeles Galaxy.

The records were hindered, thanks to a 38th-minute goal from Golden Boot-runner up, Edson Buddle; who scored a volley from a third of the pitch out that caught Kasey Keller off-guard.

The second leg of Champions League action saw the Sounders go down 1–0 to Metapán in the match, and level on aggregate, due to an 18th-minute opener from retired Panamanian international Anel Canales.

Recently acquired Álvaro Fernández tied the game in the 74th minute, to level the match at one, and to give the Sounders a 2–1 lead on aggregate.

In spite of the early goal, the Sounders could not hold the lead and relinquished it late in the first half, when Marathón's Orvin Paz leveled the game ten minutes later.

Needing a win to keep their knockout stage hopes alive, the Sounders would have to travel south to Estadio Tecnológico in Mexico to take on red-hot Monterrey.

However, a pair of quick goals from Mexican international Aldo de Nigris and Chilean-international Humberto Suazo leveled the game at two apiece.

The win gave Monterrey a guaranteed first-place finish in Group C. As a result of being knocked out the championship round in the Champions League, the Sounders began to emphasize more on the U.S. Open Cup final against Columbus and their push for the playoffs.