Christopher Chaney, 35, pleaded guilty in March to nine counts, including charges of unauthorised access to a computer and wiretapping.
He was arrested last year as part of a year-long investigation dubbed Operation Hackerazzi.
Prosecutors said Chaney illegally accessed the email accounts of more than 50 people in the entertainment industry.
Nude photos Johansson had taken of herself were later posted on the internet. The Avengers Assemble star said the photos were meant for actor Ryan Reynolds, now her ex-husband.
Federal prosecutors are recommending a six-year prison sentence.