The Sounders hired head coach Sigi Schmid, who had won the MLS Cup with the Columbus Crew in 2008, and retained Hanauer as general manager.

The club made their home debut on March 19, 2009, at Qwest Field against MLS Cup runners-up New York Red Bulls and won 3–0.

Colombian forward Fredy Montero scored 12 goals and was the team's top goalscorer; four Sounders players were also named to the All-Star Game roster.

[3] In 2008, Sounders FC developed the Starfire Sports Complex in Tukwila and the USL team played most of the 2008 season at the updated facility.

[4] In late 2008, Seattle Sounders FC interviewed several head coach candidates, including Columbus Crew manager Sigi Schmid, New England assistant Paul Mariner, and Kansas City technical director Peter Vermes.

[6] The MLS ruled that no tampering occurred, but ordered Sounders FC to financially compensate the Crew before signing Schmid.

[9][10] Retired Major League Soccer veteran defender Ezra Hendrickson joined the Sounders as an assistant coach in January, 2009.

[12] Joining Henderson in the front office is longtime Seattle Seahawks VP Gary Wright as the senior vice president of business operations.

[16] On August 14, 2008, the Sounders announced in a press conference their second signing for the 2009 season, former United States men's national team goalkeeper Kasey Keller, a Washington native.

In the expansion draft, held on November 26, 2008, Seattle Sounders FC selected the following players from other MLS teams: Nate Jaqua (Houston), Brad Evans (Columbus), Stephen King (Chicago), Jeff Parke (RBNY), James Riley (San Jose), Khano Smith (New England), Jarrod Smith (Toronto FC), Nathan Sturgis (Real Salt Lake), Peter Vagenas (LA Galaxy) and Tyson Wahl (Kansas City).

With the number one pick of the first round of the draft, Seattle Sounders FC selected University of Akron forward Steve Zakuani.

[24] FC traded a conditional draft pick to Houston in order to acquire defender Patrick Ianni, who had worked with Seattle's coach Schmid on the under-20 US national team.

[25] Seattle also traded allocation money to Toronto FC in exchange for Tyrone Marshall in order to increase their depth on defense.

[26] The Sounders also traded away midfielder Khano Smith, another expansion draft selection, to Red Bull New York for allocation money.

[28] On February 9, 2009, in their first ever exhibition game, Sounders FC beat the Los Angeles Galaxy 3–1 on a practice field beside The Home Depot Center in Carson, California.

[35] On February 28, Sounders FC had their first tie of the preseason, 1–1 against CED, a team made up of local free agent players.

Michael Fucito, Fredy Montero, Brad Evans and Zach Scott and Sebastian Le Toux all scored in the victory.

[40] On March 12, Sounders FC played their final preseason match against the Colorado Rapids of the MLS at Qwest Field.

Fredy Montero scored the first regular season goal in team history, finishing a movement from Sebastien Le Toux and Osvaldo Alonso in the 12th minute.

[44] On March 28 Sounders FC continued the success of their fast start with a second consecutive home shutout, defeating Real Salt Lake 2–0.

After winning their first three games, Seattle Sounders FC suffered their first competitive loss at home against the Kansas City Wizards.

First, a 1–1 tie at the Chicago Fire in which striker Fredy Montero was sent off in the 48th minute for an elbow to the face of Gonzalo Segares while both players went up for a ball in the air.

[54] Then another 1–1 tie the next week at home against the Los Angeles Galaxy in which yet another red card was issued, to James Riley this time, in the 57th minute for a "phantom blow" to Mike Magee as the two got into a scrum.

[56] May 31, 2009 Sounders FC then returned home for their 5th consecutive tie in league play, this time 1–1 against the Columbus Crew in which Tyrone Marshal was ejected in the 92nd minute when he threw what the referee believed was a punch at Steven Lenhart in retaliation for an elbow.

After the first 12 games of the season, Sounders FC were in 5th place overall and were tied for the league lead with 5 red card ejections and 6 disciplinary suspensions.

On June 13, in a rematch with San Jose, Sounders FC began a stretch where 4 of their next 5 games would be played in front of their home crowd at Qwest Field.

[62] The following week, in a quarterfinal match, Sounders FC defeated visiting Kansas City on a penalty kick in the 89th minute by Sebastien Le Toux.

[63] It was announced in early July that the Sounders had signed left-footed Costa Rican defender Leonardo González to help at the left back position.

[71] On August 8, Sounders FC received their third straight shutout in regular season play in a 1–0 loss at Salt Lake.

[77] On the heels of this public disagreement, D.C. United launched a marketing campaign to sell more tickets to the match which included a web site heralding the club's history of titles as an original MLS franchise, WeWinTrophies.com; an open letter placed in local newspapers declaring that D.C. fans set the standard for support in the league and that Sounders FC and its fans did not think D.C. deserved to host; videos on the team's official blog from local celebrities urging fans to attend and ticket and concession specials for the game.