In November 2013, Little left deposed champions Arsenal after six years for American National Women's Soccer League (NWSL) club Seattle Reign FC.
Laura Harvey had departed Arsenal to coach Seattle Reign the previous year and had made Little her top transfer target.
Of the signing, Harvey said, "Kim is world-class.
Her talent and proven experience will be a huge asset for our team in the coming seasons.
Having coached Kim for nearly four years, I have no doubt that her creativity and goal-scoring ability will prove an exciting proposition for the NWSL."

During her first appearance for the Reign, she scored a brace against the Boston Breakers helping Seattle win 3–0.
After scoring a league-high four goals during the month of April helping the Reign go undefeated in four games, she was named NWSL Player of the Month.
She became the first player in the history of the league to be named Player of the Month twice after earning the honour for the month of May. Her five consecutive games with goals scored during the month tied the league record previously set by Abby Wambach during the previous season.
She was named Player of the Month for a third time for the month of July after her three goals and four assists in six games helped Seattle secure a 4–1–1 record and clinch the 2014 NWSL Shield (regular season title) several weeks before the end of the season.
The Reign finished the regular season with a 16–2–6 record and 54 points – 13 points ahead of the second place team, FC Kansas City.
During the team's playoff semi-final match against Washington Spirit, Little scored one goal helping the Reign win 2–1 and advance to the championship final against FC Kansas City.
The team was defeated by Kansas City 2–1.
Little was named league MVP in her first season with the club.
Her 16 goals during the regular season also earned her the league's Golden Boot award.
Her seven assists tied for second highest in the league.

After returning to the Reign for the 2015 season, Little was the team's leading scorer with 10 goals (second in the league following Crystal Dunn with 15).
Her seven assists ranked first in the league.
The Reign finished the regular season in first place clinching the NWSL Shield for the second consecutive time.
After advancing to the playoffs, Seattle faced fourth-place team Washington Spirit and won 3–0, advancing to the championship final.
Seattle was ultimately defeated 1–0 by FC Kansas City during the championship final in Portland.
Little, along with teammates Lauren Barnes, Beverly Yanez, and Jess Fishlock, were named to the NWSL Best XI team.

During the first few months of the 2016 season, a number of offensive players became unavailable due to injury including Manon Melis, Jess Fishlock and Megan Rapinoe.
During the team's second game of the season, Little served two assists and scored a goal in the 79th minute to secure a 3–0 win against the Boston Breakers.
The following week, she scored the lone goal of the match against FC Kansas City.
Little finished the regular season with six goals and two assists.
Seattle finished the regular season in fifth place with a 8–6–8 record, narrowly missing a playoff spot by two points.

On 17 October 2016, Little announced that she would return to Arsenal L.F.C ahead of the 2017–18 FA WSL season.
Harvey said Little was given an "incredible offer" of a multi-year contract, though no other details were disclosed.
In November 2013, Little left deposed champions Arsenal after six years for American National Women's Soccer League (NWSL) club Seattle Reign FC. Laura Harvey had departed Arsenal to coach Seattle Reign the previous year and had made Little her top transfer target. Of the signing, Harvey said, "Kim is world-class. Her talent and proven experience will be a huge asset for our team in the coming seasons. Having coached Kim for nearly four years, I have no doubt that her creativity and goal-scoring ability will prove an exciting proposition for the NWSL."
During her first appearance for the Reign, she scored a brace against the Boston Breakers helping Seattle win 3–0. After scoring a league-high four goals during the month of April helping the Reign go undefeated in four games, she was named NWSL Player of the Month. She became the first player in the history of the league to be named Player of the Month twice after earning the honour for the month of May. Her five consecutive games with goals scored during the month tied the league record previously set by Abby Wambach during the previous season. She was named Player of the Month for a third time for the month of July after her three goals and four assists in six games helped Seattle secure a 4–1–1 record and clinch the 2014 NWSL Shield (regular season title) several weeks before the end of the season. The Reign finished the regular season with a 16–2–6 record and 54 points – 13 points ahead of the second place team, FC Kansas City. During the team's playoff semi-final match against Washington Spirit, Little scored one goal helping the Reign win 2–1 and advance to the championship final against FC Kansas City. The team was defeated by Kansas City 2–1. Little was named league MVP in her first season with the club. Her 16 goals during the regular season also earned her the league's Golden Boot award. Her seven assists tied for second highest in the league.
After returning to the Reign for the 2015 season, Little was the team's leading scorer with 10 goals (second in the league following Crystal Dunn with 15). Her seven assists ranked first in the league. The Reign finished the regular season in first place clinching the NWSL Shield for the second consecutive time. After advancing to the playoffs, Seattle faced fourth-place team Washington Spirit and won 3–0, advancing to the championship final. Seattle was ultimately defeated 1–0 by FC Kansas City during the championship final in Portland. Little, along with teammates Lauren Barnes, Beverly Yanez, and Jess Fishlock, were named to the NWSL Best XI team.
During the first few months of the 2016 season, a number of offensive players became unavailable due to injury including Manon Melis, Jess Fishlock and Megan Rapinoe. During the team's second game of the season, Little served two assists and scored a goal in the 79th minute to secure a 3–0 win against the Boston Breakers. The following week, she scored the lone goal of the match against FC Kansas City. Little finished the regular season with six goals and two assists. Seattle finished the regular season in fifth place with a 8–6–8 record, narrowly missing a playoff spot by two points.
On 17 October 2016, Little announced that she would return to Arsenal L.F.C ahead of the 2017–18 FA WSL season. Harvey said Little was given an "incredible offer" of a multi-year contract, though no other details were disclosed.
Kim Little