Boston has bet big on the American goalkeeper, signing Murphy through the 2029 NWSL season with a mutual option for 2030 for what a source told ESPN is worth $1.5 million total guaranteed.
Murphy signed with the 2026 NWSL expansion side as a free agent earlier this year, as ESPN first reported in October.
Legacy FC confirmed the signing of Murphy on Monday.
Murphy joined the North Carolina Courage since the 2021 season and soon became a regular with the U.S. women's national team.
She was the backup USWNT goalkeeper to Alyssa Naeher at the 2023 World Cup and the 2024 Olympics, where the Americans won a gold medal.
Murphy has 20 caps for the United States, although she has not appeared for the team since October 2024.
"Casey's track record gives her a strong foundation for this next chapter in Boston," general manager Domè Guasch said in a statement. "Beyond her quality as a goalkeeper, Casey is a true leader. We believe this will be a great addition as we build our first roster for 2026."
In North Carolina, Murphy became the all-time leader in regular-season wins for a historically successful Courage team. She arrived in North Carolina from Seattle Reign FC (then named OL Reign) via a multi-team trade that eventually sent U.S. defender Crystal Dunn to the Portland Thorns FC.
Murphy had spent two seasons with the Reign after electing to begin her career abroad.
Murphy was selected No. 13 overall in the 2018 NWSL Draft by NJ/NY Gotham FC (then named Sky Blue FC) but, despite playing on the same home field for Rutgers University, decided to sign with Montpellier in France.
"I'm excited to be in such a sports city," Murphy said in a statement. "They call it 'Title Town' for a reason, and I'm excited to build a culture here from the ground up and be a part of something new.
"There's a lot of exciting energy and ambition around this team that drew me to it, and I'm just looking forward to putting my leadership skills on display and setting the standard each day for my teammates and meeting new people and getting involved in the community as well."
Boston has announced a handful of players thus far ahead of the team's 2026 launch.
Last week, the team also announced the signing of goalkeeper Hannah Stambaugh, who joined as a free agent from Angel City FC.
Brazilian forward Amanda Gutierres, who finished 21st in the 2025 Ballon d'Or vote, is Boston's other big signing to date.
The 24-year-old arrived on a pre-transfer from Palmeiras.
Legacy FC and Denver Summit FC will both begin play in 2026, bringing the NWSL to 16 teams.
