Iler, who plays mob boss Tony Soprano's son AJ on the HBO hit TV show, admitted he was involved in the mugging of two tourists in Manhattan last July 4, saying he and friends had decided to "hassle" the two teenage victims.
Police picked up Iler just a few blocks from the scene of the crime.
Iler could have faced up to 15 years' imprisonment if he had stood trial and been convicted of the original, more serious charge of second-degree robbery.
Alban Selimaj, a co-defendant who's also 17, entered into the same plea agreement with prosecutors. There are two other defendants: a teen whose case is being handled in family court because he was 15 at the time, and 20-year-old Michael Cournede, who has pleaded innocent and will stand trial on the robbery charge.