Toronto was ineligible to qualify through the berth, which belongs to the United States Soccer Federation, but participated in the 2018 CONCACAF Champions League after winning the Canadian Championship.

[15] Toronto immediately jumped into a run of good form, with only three losses in the first half of the season, and remained near level with Chicago Fire at the top of the league.

[20] In the conference finals, Toronto traveled to play Columbus Crew SC, earning a 0–0 away draw and a 1–0 win at home, qualifying them for the MLS Cup.

[22] Head coach Brian Schmetzer, promoted from his interim role, made offseason roster changes to replace older veteran players with younger talent that align with general manager Garth Lagerwey's vision for the club.

[27] From late June to early September, the team welcomed back injured players and went on a 13-match unbeaten streak that put them in playoff contention.

[28] The streak ended with a series of draws and losses,[29] but the Sounders recovered with three wins in late September and October to clinch a second-place finish in the Western Conference.

[40] For ESPN, Adrian Healey, Taylor Twellman, and Julie Stewart-Binks called the match, with pre-game and post-game coverage conducted by Max Bretos, Kasey Keller, and Alejandro Moreno.

[41][42] For TSN, Luke Wileman and Steven Caldwell called the match, with pre-game and post-game coverage conducted by James Duthie, alongside Terry Dunfield and Kristian Jack.

[45] The ESPN and Spanish language broadcasts in the United States drew an audience of 1.1 million combined viewers, a 43 percent decline from the 2016 final.

[49] The Sounders were without injured captain Osvaldo Alonso,[50] and also chose to start Joevin Jones at left back in place of Nouhou Tolo.

[52] Toronto continued its control of possession and attacking chances early in the second half, with Frei making two key saves on shots from Michael Bradley and Giovinco after the hour mark.

[56] During a corner kick for the Sounders in the 83rd minute, a wire holding the Skycam system over the stadium fell onto the pitch, causing a short delay.

[56] Both teams made their final substitutions early in stoppage time, with Toronto bringing on Benoît Cheyrou for Marky Delgado and Seattle switching Jones with Nouhou.

[56] MLS Cup Most Valuable Player Jozy Altidore (Toronto FC) Assistant referees Adam Wienckowski (United States) Jeremy Hanson (United States) Fourth official Kevin Stott (United States) Fifth official Danny Thornberry Video assistant referee David Gantar (Canada) Match rules Toronto FC became the first Canadian team to win the MLS Cup, and the first MLS team to complete a domestic treble, after winning the Canadian Championship and Supporters' Shield earlier in the season.

[63] The day after the final, The Seattle Times mistakenly ran pre-scheduled advertisements on its website that promoted a victory parade and rally for the Sounders, which were later removed.

[66] It was the second victory parade held in the city in as many weeks, as the Toronto Argonauts had won the Canadian Football League's Grey Cup in November.