The Portland Thorns drew 16,479 fans to their first home game on April 21, 2013, setting a new standard for women’s club soccer in the United States. Since then, the Thorns have developed into the best fan-supported women’s soccer club in the world and one of the most successful clubs in National Women’s Soccer League (NWSL) history.

The Thorns were founded in November 2012 after U.S. Soccer President Sunil Gulati asked Merritt Paulson, an owner of the Portland Timbers, to form a women's club. With the NWSL scheduled to begin play in 2013, Gulati believed that bringing a current Major League Soccer (MLS) owner into the fold would give the league immediate stability.

Paulson became the first MLS owner to form a top-flight women’s soccer club. The partnership with the Timbers enabled the Thorns to hit the ground running in their inaugural season, as they came into the league with built-in facilities and infrastructure. The Thorns drew a league-best 13,320 fans per game in 2013 to home matches at Providence Park, the city-owned stadium the club shares with the Timbers. The other seven clubs in the league combined averaged 2,980 fans per game in 2013.

The Rose City Riveters, the supporters’ group for the Thorns, was formed ahead of the inaugural season with the help and support of the Timbers Army, the longtime supporters’ group for the Timbers. The Rose City Riveters quickly became known for their tifos—displays that fans raise in the stands ahead of games—as well as orchestrated chants and the red smoke bombs they light after each goal. Portland has drawn more than 15,000 fans per game in five separate seasons (2015–2019). In 2019, the Thorns led the NWSL in average attendance for the seventh straight year, averaging 20,098 fans per game.

Two previous top-flight women’s soccer leagues in the United States suspended operations after just three seasons—the Women’s United Soccer Association (WUSA) began play in 2001 and folded in 2003 and Women’s Professional Soccer (WPS) began play in 2009 and folded after the 2011 season. The fan support in Portland, however, helped keep the NWSL going as the Thorns, the only profitable club in the NWSL's first season, agreed to share profits with the rest of the league. Since 2013, four other NWSL clubs—Houston Dash, Orlando Pride, Utah Royals, and North Carolina Courage—have partnered with professional men’s clubs, benefiting from the infrastructure and financial and staffing support that an established organization can provide. 

While Portland’s success off the field has set the Thorns apart in women’s sports, the club has also excelled on the field. The club’s first coach, Cindy Parlow Cone, a former star with the U.S. Women’s National team, led the club to the inaugural NWSL Championship in 2013 when the Thorns beat the Western New York Flash 2-0 on the road to claim the title. Cone left the club after one season and was replaced by Paul Riley, who had two unsuccessful years with the Thorns before parting ways with the club.

Mark Parsons, who took over as head coach in 2016, led the Thorns back to the top of the NWSL. Portland won the 2016 NWSL Shield, awarded to the club with the best record in the regular season, before beating the North Carolina Courage 1-0 in Orlando to claim the 2017 NWSL Championship title. Portland reached the title game again in 2018, but lost 3-0 to the Courage at Providence Park. In 2019, the Thorns had their worst campaign since 2015, reaching the playoffs but falling 1-0 on the road to the Chicago Red Stars in the semifinals.

The Thorns have lured top players in women’s soccer to Portland, including World Cup champions Alex Morgan, Tobin Heath, Lindsey Horan, Meghan Klingenberg, Emily Sonnett, and Adrianna Franch; Canada Soccer’s Women’s National Team captain Christine Sinclair; and renowned French midfielder Amandine Henry. In 2018, Horan was the first Thorn to claim the NWSL Most Valuable Player Award.

The Thorns organization has been active in promoting youth soccer in Oregon and southwest Washington. The Timbers and Thorns announced a ten-year partnership with the Oregon Youth Soccer Association (OYSA) in 2014, agreeing to provide staff and financial resources to support OYSA teams. In June 2016, U.S. Soccer announced that the Thorns would be included as one of twenty-five inaugural clubs in their Girls' Development Academy program. The Thorns launched its academy program in the fall of 2017, giving top girls' soccer players in the Oregon and southwest Washington area a platform to hone their skills and a pathway to compete at a higher level.

In September 2021, former Thorns players Mana Shim and Sinead Farrelly came forward in an article in the Athletic against former coach Paul Riley, alleging sexual misconduct and coercion. The Athletic reported that the Thorns had received a complaint from Shim in 2015 and had fired Riley, but at the time the Thorns told the public he was fired for poor results. Riley was allowed to continue coaching in the NWSL and was fired as head coach of the North Carolina Courage after the Athletic article was published. 

 In October 2021, the U.S. Soccer Federation released a report from an independent investigation, led by former U.S. Deputy Attorney General Sally Yates, into charges of sexual misconduct in the Timbers/Thorns organization. The report detailed serious allegations against multiple coaches, raised questions about accountability and player safety, and described a culture that allowed the abuse of players and inappropriate comments to female employees. It also shed a light on how the club had dismissed Shim's complaint and the role that General Manager Gavin Wilkinson and owner Merritt Paulson played in promoting Riley and helping him get hired elsewhere in the NWSL. Paulson fired Wilkinson and President of Business Operations Mike Golub and stepped down as CEO of the organization. He continues as owner of both the Thorns and the Timbers.