Harrison was drafted 12th overall by the Phoenix Mercury in the 2015 WNBA draft. She sat out the 2015 season due to a torn ACL while playing in her senior year at Tennessee. She would make her debut in 2016. In her rookie season, she averaged 3.1 ppg and 1.8 rpg in 26 games as a reserve for the Mercury.
On May 16, 2019, Harrison was traded to the Dallas Wings.[3]
Harrison signed with the Chicago Sky on February 2, 2023 during free agency.[4] She was sidelined for her entire first season with a torn left meniscus that required surgery.[5]
Harrison signed with the New York Liberty on February 21, 2025 in open free agency.[6][7][8]
In February 2024, Harrison joined the WNBA Changemakers Collective and their collaboration with VOICEINSPORT (VIS) as a mentor, "aimed at keeping girls in sport and developing diverse leaders on the court and beyond the game."[12][13]
^Taylor, Shakeia; Poe, Julia (February 4, 2023). "Isabelle Harrison signing with the sky". The Times. Munster, Indiana: Chris White, Lee Enterprises. p. C6. Retrieved February 21, 2025.
^Jones, Siera (February 21, 2025). "Isabelle Harrison Joins Reigning WNBA Champion New York Liberty". Athletes Unlimited. Retrieved February 21, 2025. 'We are excited to welcome Izzy Harrison to the Liberty family and look forward to the positive impact she will have on and off the court,' said Liberty Head Coach Sandy Brondello.
^"New York Liberty Sign Isabelle Harrison". Liberty.WNBA.com. New York, NY: NBA Media Ventures, LLC. February 21, 2025. Retrieved February 21, 2025. Sandy Brondello said, 'Having originally drafted her with Phoenix, she has consistently demonstrated the ability to impact games on both ends. Izzy's versatility and commitment strengthens our post rotation and makes her an ideal fit for our team as we pursue another championship in 2025.'
^"Transactions". WNBA. NBA Media Ventures, LLC. February 21, 2025. Retrieved February 21, 2025. Isabelle Harrison signed a Training Camp Contract with the New York Liberty.