The suit was filed Monday in state Supreme Court in Manhattan.
Plaintiff Justin Henry says he was never paid for the office work he performed from October 2007 through May 2008 but should have been under state labour law.
The suit alleges there was no academic or vocational training as part of the internship, and that employees would have needed to be hired to do the work if Henry wasn't doing it for free.
Atlantic is part of Warner Music Group. Warner declined to comment on pending litigation.
Similar lawsuits over unpaid internships have been filed in other industries like magazine publishing.