Boudri is leaving MLS club Los Angeles FC, where he moved before the season.
"The feeling is great. That's why I chose to come to Hammarby, because I felt this was right," Amin Boudri says on the Stockholm club's website.
According to Aftonbladet, the signing was the most expensive in Allsvenskan history. Boudri is said to have cost Hammarby around 37 million kronor.
During his time at Gais, Boudri scored eight goals and had two assists in 48 games.
"It obviously feels fantastic to have Amin on board with us. Amin's profile is exactly what we have been looking for," Hammarby sports director Mikael Hjelmberg says.
Boudri can make his debut for "Bajen" as early as Thursday, in the Europa League qualifying match against Anderlecht, as the transfer was registered just before midnight.
