In February 2013, Marshall signed with Portland Thorns FC for the inaugural season of the National Women's Soccer League.
She was on the starting lineup as a defender in all of the Thorns' 22 games as the team finished third in regular season play and received a berth to the playoffs.
During the team's playoff semi-final match, Marshall served the assist to Tiffany Weimer's equalizer goal.
The Thorns would eventually defeat FC Kansas City 3-2 in overtime.
The Thorns defeated Western New York Flash during the playoff final clinching the league's first championship title.

Marshall was waived by the Thorns during the post-season and picked up during the waiver draft by the Washington Spirit.
A few months later, she was traded to the Seattle Reign FC.
In December 2013, she was traded back to the Portland Thorns.
Thorns management clarified that Marshall was put on waivers due to a cap issue.
With the trades, she was signed to a new contract at a different salary for the 2014 season.

During the 2014 season, Marshall started in all 24 matches for the Thorns playing for 2072 minutes.
After finishing third during the regular season with a 10–8–6 record, the Thorns advanced to the playoffs where they were defeated in the semifinals 2-0 by eventual champions FC Kansas City.

In August 2014, Marshall suffered an anterior cruciate ligament (ACL) tear during a match against the Seattle Reign .
She announced her retirement in February 2015, citing low pay.
In February 2013, Marshall signed with Portland Thorns FC for the inaugural season of the National Women's Soccer League. She was on the starting lineup as a defender in all of the Thorns' 22 games as the team finished third in regular season play and received a berth to the playoffs. During the team's playoff semi-final match, Marshall served the assist to Tiffany Weimer's equalizer goal. The Thorns would eventually defeat FC Kansas City 3-2 in overtime. The Thorns defeated Western New York Flash during the playoff final clinching the league's first championship title.
Marshall was waived by the Thorns during the post-season and picked up during the waiver draft by the Washington Spirit. A few months later, she was traded to the Seattle Reign FC. In December 2013, she was traded back to the Portland Thorns. Thorns management clarified that Marshall was put on waivers due to a cap issue. With the trades, she was signed to a new contract at a different salary for the 2014 season.
During the 2014 season, Marshall started in all 24 matches for the Thorns playing for 2072 minutes. After finishing third during the regular season with a 10–8–6 record, the Thorns advanced to the playoffs where they were defeated in the semifinals 2-0 by eventual champions FC Kansas City.
In August 2014, Marshall suffered an anterior cruciate ligament (ACL) tear during a match against the Seattle Reign . She announced her retirement in February 2015, citing low pay.
Nikki Marshall