The actor's role in the sequels were in doubt as Marvel was reportedly unwilling to agree to his pay demands.
But Robert and the studio have come to an agreement which will see him reprise the role of Tony Stark/Iron Man in The Avengers 2 and The Avengers 3, reported Ace Showbiz.
A statement on Marvel's website said, "I am Iron Man. Tony Stark's famous closing line to the very first Iron Man film takes on new life today as Marvel is pleased to announce the signing of Robert Downey Jr to reprise the role of the 'billionaire, genius, playboy, philanthropist'."
Under the two-picture agreement, Downey will star as Tony Stark/Iron Man in The Avengers 2 and The Avengers 3.
The sequel will start production in March 2014 and is being written and directed by Joss Whedon.