The British star, who became famous with 'Bend It Like Beckham', went on to star in umpteen period dramas 'Anna Karenina', 'Pride & Prejudice' and 'Pirates of the Caribbean'.
In 'Begin Again' she will be seen in a grungy dive bar musician avatar.
Asked whether she was trying to move away from period dramas, the actress said, "I definitely wanted to do something different. I wanted to do a role where I certainly don't die in the end. May be, it will be nice to have a happy ending.
'Begin Again' also stars Mark Ruffalo and is the debut film of pop rock band Maroon 5's lead singer, Adam Levine.
Directed by John Carney, the film is a soul-stirring comedy about what happens when lost souls meet.
Knightley plays Greta while Levine plays Dave, her long-time boyfriend.
Greta is left alone after Dave, who lands a major record deal, leaves her for fame but Greta's world takes a turn for the better when Dan (Mark Ruffalo), a disgraced record-label exec, stumbles upon her performing and is immediately captivated by her raw talent.
