Established in 2012, the team began play in 2013 in the then-eight-team NWSL, which received support from the United States Soccer Federation (USSF).

This precursor to the NWSL announcement the following November was to facilitate an integrated development structure for Oregon's girls youth soccer to elite women's competition.

[11][12][13] The formation of the National Women's Soccer League (NWSL) was announced on November 21, 2012, with Portland selected as a host for one of the eight teams.

[21] The other players assigned to the Thorns were Rachel Buehler, Tobin Heath, Karina LeBlanc, Alex Morgan, Marlene Sandoval, and Luz Saucedo.

Under head coach Parlow Cone, the Thorns played in the new league's inaugural game on April 13, 2013, against host team FC Kansas City, which ended in a 1–1 draw.

[24][25] The team's first home match on April 21 provided the club its first victory, a 2–1 win over Seattle Reign FC.

[26] Beyond setting a new league record, the opening day crowd of 16,479 at Jeld-Wen Field eclipsed any single-game attendance from Women's Professional Soccer.

[29] The Thorns kicked off their 2014 season with the announcement of a new head coach, Paul Riley, formerly of the Long Island Fury of the Women's Premier Soccer League.

[33] The Thorns also sold out Providence Park for the first time in a match against Seattle Reign FC following the 2015 FIFA Women's World Cup, again setting the league's attendance record with 21,144.

[37] In Parsons's first season in charge, the Thorns executed a series of trades — anchored by moving founding forward Alex Morgan and midfielder Kaylyn Kyle to expansion team Orlando Pride — that resulted in the acquisitions of Emily Sonnett, Lindsey Horan, Meghan Klingenberg, Adrianna Franch, Dagný Brynjarsdóttir, Amandine Henry, and Nadia Nadim.

[38][39][40][41] The acquisitions would form the core of a team that won the Thorns its first NWSL Shield in 2016 and host its first playoff match, against Western New York Flash led by their former coach Paul Riley.

[3] Despite losing Henry and Nadim for the 2018 season due to financial limits[43] and trading founding midfielder Allie Long to Seattle Reign FC for the rights to Caitlin Foord,[44] the Thorns finished 2018 again in second place behind the Courage.

[49] Beginning September at the top of the table, the team entered the worst run of form in Parsons' tenure as head coach, losing three of its last five games, including an embarrassing club-worst 6–0 loss to the Courage.

[52] The Thorns finished last in the inaugural NWSL Challenge Cup's group stage but upset the top-seeded Courage in the quarterfinals before losing to eventual champions Houston Dash in the semifinals.

[53] The Thorns also participated in and clinched the 2020 NWSL Fall Series Community Shield with a win on October 11, 2020, over OL Reign.

[62] President of business Mike Golub, separately accused of sexual harassment of Parlow Cone in the report, was also fired, and Paulson stepped down as CEO of both the Thorns and Timbers.

[64] On the pitch, the Thorns won the West Division of the 2021 NWSL Challenge Cup and hosted the finals in May 2021, defeating NJ/NY Gotham FC 6–5 in a penalty shoot-out following a 1–1 draw in regulation.

[72] The next day, Rhian Wilkinson resigned as coach[73] after reports that she exchanged messages of romantic feelings with a Thorns player.

[78] On March 27, 2024, Sophia Smith was signed by the Thorns to a two-year contract extension that made her the highest paid player in the NWSL, though her salary was not disclosed.

The playoff loss would be the final match of Sinclair's professional career[85] and the end of LeBlanc's tenure as general manager.

Its design originally featured the team colors of red, black, and white "with a protective wreath of thorns surrounding a familiar, stylized rose in the center."

[103] The large crowds attended despite Timbers front office expectations of 7,000 fans per match and little promotion before the team's launch.

[115][122] Several players have played for both teams, including Allie Long, Michelle Betos, Ifeoma Onumonu, Steph Catley, Jodie Taylor, Adelaide Gay, Amber Brooks, Jessica McDonald, Danielle Foxhoven, Alyssa Kleiner, Kaylyn Kyle,[115] Tobin Heath,[123] and Emily Sonnett.

[124] On the pitch, some of the league's highest-stakes matches were contested between the Thorns and Western New York Flash, who were relocated in 2017 to become the North Carolina Courage.

[129] In the 2016 semifinals, the Thorns were the shield winners and the Flash were the lower seed, and the match was the first home playoff game for Portland.

But the Flash — who had hired former Thorns head coach Paul Riley at the start of the season — defeated Portland after extra time in a 4–3 match that featured three goals after the 90th minute.

[131] The Thorns won their revenge in the 2017 championship match, defeating the Courage 1–0 after a match that Thorns defender Meghan Klingenberg called "the ugliest soccer game I have ever played in" and featured tackles on United States national teammates and opposing club players Taylor Smith and Tobin Heath that both attempted to play through[132] but would rule both players out of national team camp in the following weeks.

[133] Adding to the rivalry was Courage defender Jaelene Daniels's 2018 appearance on The 700 Club about refusing to wear LGBT pride-themed uniforms for the United States national team and being excused from its roster citing "personal reasons",[134] and the relocation of a Courage 2018 playoff match to Portland from Cary, North Carolina due to Hurricane Florence.

Providence Park was expanded in 2019 to a seated capacity of 25,218, making it the second-largest NWSL venue at the time behind Orlando Pride's Exploria Stadium (25,527).

[147] The Thorns set the NWSL's all-time attendance record several times in Providence Park starting from its home opener on April 21, 2013 (16,479),[148] and twice at the venue's capacity on July 23, 2015 (21,144)[149] and August 11, 2019 (25,218).