The 2. Bundesliga champions have already snapped up Sebastian Langkamp from Augsburg and on Tuesday confirmed the acquisition of 26-year-old midfielder Hosogai, who has agreed a four-year deal.
"Hertha BSC has taken the 18-time Japan international Hajime Hosogai under contract," the club said in a statement.
"The 26-year-old midfielder, who is joining from Bayer Leverkusen, has signed a contract in Berlin for the next four years. All parties have agreed on transfer arrangements between the clubs."
Hosogai joined Leverkusen from Urawa Red Diamonds in 2011. He played 39 games on loan at Augsburg before making 14 appearances for Leverkusen this past season.