The experienced RB Leipzig midfielder will undergo a medical before joining the club's pre-season camp in Portugal.
The 28-year-old, whose contract with the Bundesliga side expired at the end of June, is expected to sign a two-year deal with the option of a further 12 months. Leipzig had hoped to retain their vice-captain, but Schlager has opted for a new challenge in the Premier League.
The move reunites Schlager with new Forest head coach Oliver Glasner, who previously worked with the midfielder at Wolfsburg after bringing him to the club from Red Bull Salzburg in 2019. It also represents Glasner's first signing since taking charge at the City Ground earlier this month.
Schlager arrives with a wealth of experience, having made more than 100 appearances for Leipzig since joining in 2022, while also enjoying spells with Salzburg and Wolfsburg. He has earned 55 caps for Austria and started all four of his country's matches at the 2026 World Cup before they were knocked out by Spain in the round of 32.
Forest view the midfielder as an ideal addition after the departure of Elliot Anderson, who joined Manchester City recently in a big-money transfer. Although Schlager is expected to fill much of the void left by Anderson's exit, the club are reportedly still considering further midfield reinforcements before the transfer window closes.
His arrival adds proven Bundesliga and international pedigree to a squad that already includes Ibrahim Sangare, Nicolas Dominguez, Ryan Yates, Morgan Gibbs-White and James McAtee.
Forest are also expected to remain active elsewhere in the market as Glasner shapes his squad for the new Premier League season, with defensive reinforcements among the club's priorities.
