Parker Romo, who went 5-for-5 last week for the Falcons, will officially replace Koo as the team's lone kicker.
Koo leaves Atlanta as the team's third all-time leader in points with 700.
"I want to thank the Falcons organization for giving me an opportunity when no one else would six years ago," Koo posted on Instagram Friday. "This place helped me grow as a kicker and as a man. I will forever be grateful for the support from the fans during my time here. I have nothing but love and respect for everyone in the building. I wish y'all the best. I'm full of gratitude and excitement as I continue my journey in this league."
The South Korean native is a former Lou Groza (best college kicker) who originally signed as an undrafted free agent with the Los Angeles Chargers in 2017, with whom he played for only four weeks before being waived.
He spent a year away from football following his release, and signed to the Atlanta Legends (AAF) in 2019 before eventually finding his way onto the Falcons roster, where he would become a sensation for the team.
Koo made 23-of-26 field goal attempts in 2019 for the Falcons before eventually being selected to his first, and only, Pro Bowl a year later.
He led the league with 37 field goals (39 attempts), putting up a career high 94.9% field goal percentage. Unfortunately for Koo, the numbers started to slip from there. Koo made 27-of-29 (93.1%) in 2021, still proving to be one of the best kickers in the game.
From there on, Koo never reached above a 90% again. He went 32-of-37 (86.5%) in back-to-back years (2022-2023) before having the worst season of his career last season - hitting just 24-of-35 (73.5%).
The 31-year-old kicked in just one game this season for the Falcons, going 2-of-3.