in 2019
Chicago Sky (2019) Samuelson was drafted 4th overall by the
Chicago Sky in the
2019 WNBA draft, with whom she spent her rookie season. Across 20 games, she averaged 2.4 points, 0.9 rebounds, and 0.4 assists during 7.7 minutes per game.
Dallas Wings and Perfumerías Avenida (2020-2021) Samuelson was traded to the
Dallas Wings for
Azura Stevens on February 14, 2020, making Katie Lou and her sister
Karlie teammates for the first time as professionals. However, Karlie was waived before the season began. The sisters still wound up playing together in Spain as Samuelson signed with Karlie's team
Perfumerías Avenida. Samuelson helped Avenida win
the Spanish championship and finish second in the continental
EuroLeague, being listed on the team of the tournament in both championships.
Seattle Storm (2021) Samuelson was traded on February 10, 2021, to the
Seattle Storm for the number one overall pick in the
2021 WNBA draft, who became
Charli Collier. While with Seattle, Samuelson became a full-time starter for the first time in her career, having started 24 of the 27 games she played for them while averaging career highs of 7 points, 3.5 rebounds, and 1.7 assists per game. Katie Lou’s sister Karlie later joined the Storm and played three games with them in August and September 2021.
Los Angeles Sparks (2022) Her tenure with the Storm ended on February 3, 2022, when she and the
2022 WNBA draft ninth pick were traded to the
Los Angeles Sparks in exchange for
Gabby Williams. Samuelson was a teammate with Williams for three years at UConn and both women were selected fourth overall by the Chicago Sky in consecutive years, Williams having been picked in 2018.
Indiana Fever (2024) , (right) during a game in 2024 After not playing the
2023 season due to her pregnancy, Samuelson signed with the
Indiana Fever prior to the
2024 WNBA season on February 1, 2024. On February 10, 2025, Samuelson was waived by the Fever and signed a mutual contract termination agreement with the team.
Phantom BC and second stint with Seattle Storm (2025–present) On December 20, 2024, it was announced that Samuelson had signed with
Phantom BC (filling their wildcard spot) for the
inaugural 2025 season of
Unrivaled, the women’s 3-on-3 basketball league founded by
Napheesa Collier and
Breanna Stewart. On February 21, 2025, Samuelson signed with the Seattle Storm for a one-year deal, returning to the franchise after four years. On May 3, 2025, the Storm announced that Samuelson sustained a right
ACL tear during practice on May 1. After missing the
2025 season, it was announced in April 2026 that she had been re-signed by the Storm. ==Career statistics==