Bruins general manager Peter Chiarelli announced in a statement the base salary for the contract is worth $1.8 million US, but it carries incentives of $4.2 million for a cap hit of $6 million.
While Boston was mentioned among the frontrunners for Iginla's services when he was rumoured to be on the trading block, the Pittsburgh Penguins swooped in and acquired the 36-year-old from the Calgary Flames in late March to bolster their playoff push.
However, it was the Bruins who got the last laugh in the 2013 post-season by sweeping Iginla and the Penguins in the Eastern Conference final.
Boston went on to lose the Stanley Cup final in six games to the Chicago Blackhawks.
The move will likely help fill the gap left by the departed Nathan Horton, who left via free agency to join the Columbus Blue Jackets on a seven-year pact. Boston also made a massive swap on Thursday, acquiring Loui Eriksson, Reilly Smith, Joe Morrow and Matt Fraser in a deal that sent Tyler Seguin, Rich Peverley and Ryan Button to the Dallas Stars.
Iginla spent the first 16 seasons of his NHL career with the Calgary Flames and led them to Game 7 of the Stanley Cup final in 2004 when they lost to the Tampa Bay Lightning.
The six-foot-one, 207-pound Edmonton native scored 14 goals last season and 19 assists in 44 games. In 1,232 regular season contests, the six-time all-star has 530 goals and 1,106 points and is a plus-48.
He is a two-time 50-goal scorer and won the Rocket Richard Trophy (2002, 2004) as the league's top goal-scorer. Originally drafted in the first round (11th overall) in 1995 by the Dallas Stars, he also won the Art Ross Trophy in 2002.