For Ladd, who was a restricted free agent, the Blackhawks acquired defenceman Ivan Vishnevskiy and a second-round pick in 2011.
The 24-year-old Ladd has played on two Stanley Cup winners in his young career. He came to the Blackhawks from Carolina in a 2008 trade for centre Tuomo Ruutu.
Ladd missed the first three games of the final and then returned for the last three while playing with a fractured shoulder and torn ligaments against the Flyers. He was also on a Stanley Cup winner with Carolina in 2006.
Ladd had 37 goals and 62 assists in 184 regular-season games over parts of three seasons with the Blackhawks, including 17 goals and 21 assists last season.
In 36 playoff games for the Blackhawks over the past two seasons, he had six goals and four assists.
Vishnevskiy, 22, had two assists in five games with the Dallas Stars over the past two seasons. He spent most of last season in the American Hockey League with the Texas Stars and Chicago Wolves. He was acquired by the Thrashers from the Stars last February.