Miami just added another major signing, by convincing free agent guard Ray Allen to sign for the Heat, and snub the Boston Celtics.

Allen, who rejected a bigger offer from the Celtics, informed both teams Friday night of his decision, after thinking things over, according to ESPN.com. The Heat had made a presentation to Allen on Thursday.

It is understood Allen will accept Heat's mid-level exception which starts at $3.09 million and can be worth a maximum $9.5 million over three years.

Celtics had offered Allen a two-year deal worth double the amount at $12 million, including a no-trade clause.

Allen's new Heat team-mates LeBron James and Dwyane Wade welcomed the 36-year-old via Twitter.

"#HeatNation please welcome our newest teammate Ray Allen #Wow #JesusShuttlesworth," James tweeted on Friday night.

"HeatNation continues to grow," Wade added.

The deal will be made official on July 11, once the league's moratorium is lifted.

According to multiple league sources, Allen had grown frustrated with the Celtics management after he was offered in trade talks and then was replaced in the starting line-up for the younger Avery Bradley. Allen also reportedly saw his relationship with star point guard Rajon Rondo deteriorate.

While the Celtics have already got a verbal commitment from Jason Terry, but the Celtics tried to convince Allen the two could play together. Allen, however, chose to sign for the Heat after Pat Riley, Erik Spoelstra and Alonzo Mourning convinced the soon-to-be 37-year-old on the advantages of playing with James, Wade and Chris Bosh.

Miami still have three spots left in their roster and are trying to bring in veteran forwards Marcus Camby and Rashard Lewis, with both players set to hold talks with the Heat over the weekend.