The Sounders played their inaugural match on March 19, 2009, in front of a sold-out crowd of 32,523, defeating the New York Red Bulls 3-0. Seattle was the first MLS expansion team to win its first three matches, and they did so with a shutout in each.

The logo incorporates the Space Needle, an internationally recognized Seattle landmark. Built to withstand winds of up to 200 mph (320 km/h) and earthquakes of up to 9.0 magnitude, the Space Needle features an observation deck 520 ft (160 m) above ground, providing views of the downtown Seattle skyline, the Olympic and Cascade Mountains, Mount Rainier, Mount Baker, Elliott Bay, and various islands in Puget Sound.

After declining offers from two English clubs so he could sign with Major League Soccer, Steve Zakuani provided a much-needed attacking presence from the wing and was the third-best Seattle scorer with four goals throughout the regular season. The press considered him a candidate for Rookie of the Year, but the award eventually went to Omar Gonzalez.

Fredy Montero made his MLS debut on 19 March 2009, in the 2009 season opener against the New York Red Bulls, and scored the first and third goals in Seattle Sounders FC club history. Montero was named the MLS Player of the Week for the first week of the 2009 MLS season for his two goals.

The official team colors are Sounder Blue (signifying the waters of the Puget Sound), Rave Green (representing the forests of the Pacific Northwest), and Cascade Shale (representing the Cascade Range to the east of Seattle).

Kasey Keller was the starting goalkeeper for the Sounders' first-ever match, on March 19, 2009, which the the club won 3-0. He continued to have a clean sheet in each of his next three starts. His clean sheet streak came to an end on May 2, 2009, at 457 minutes in the second half of a game against the Chicago Fire.

His nickname, "The Flea", stems from his small frame and his ability to get past defenders with great ball control.

The team qualified for the MLS Cup Playoffs in each of its first 12 seasons, setting the record for consecutive playoff appearances.

Drew Carey, a stand-up comic and star of The Drew Carey Show, is regarded as one of American soccer's most recognizable supporters. He was involved with the Sounders early as a minority owner, along with Microsoft co-founder Paul Allen.

It's doubtful many soccer fans had heard of Obed Vargas before July 22, 2021, when he was one of four players called in from Sounders FC reserve team Tacoma Defiance on an extreme hardship waiver. Most probably thought he wouldn't see the field unless there was a drastic emergency, but that wasn't the case as the Sounders started five teenagers, including Vargas, who became the third-youngest player in league history to either start or play in a match at 15 years and 351 days. During his MLS debut, Vargas got to share the field with Raul Ruidiaz, one of his favorite players growing up. His family said it was a surreal moment to see Vargas on the field when Ruidiaz scored the game-winning goal to defeat Austin FC 1-0.