The deal was completed before the holiday roster freeze at midnight ET Tuesday but wasn't announced until Wednesday. Flyers GM Paul Holmgren said he's happy to get a young forward who has posted solid offensive numbers over his career.
"We think that he is going to upgrade our offence," Holmgren said in a release. "He is a player who is a right-handed shot, can play centre or right wing and he gives us a little more versatility and a little more scoring.
"He is a highly competitive player."
York, a five-foot-10 185-pound native of Waterford, Mich., recorded six goals and seven assists for 13 points and 14 penalty minutes in 32 games for the Islanders this season.
"It is always a little bit of a shock when you first get traded," said York. "I'm going to a new team and getting a new start, so I am excited about that. Hopefully, I can help turn the Flyers around in a positive way.
"I'm a fresh face and new blood coming in here. I have been in this situation before. We still have over half the season to play. There's a long way to go, so hopefully I can help the team improve."
A seven-year NHL veteran, the 28-year-old York has registered 117 goals and 183 assists for 300 points and 123 penalty minutes in 481 career regular season games with the Islanders, New York Rangers and Edmonton Oilers.
Robitaille, 31, registered five goals and 12 assists for 17 points and 22 penalty minutes in 28 games for the Flyers this season. The Ottawa native was signed as a free agent by the Flyers last July.
"We're very happy to acquire a strong playmaker in Randy Robitaille," said Islanders GM Garth Snow. "Randy will help us on the power play and he's good on faceoffs. We add another draft pick, which is always good news.
"And while we acquire a player in Randy whose production is equal to Mike's, we also gain additional cap flexibility."
Robitaille played in 10 regular season games and five playoff games for the Islanders at the end of the 2002-03 season. Over parts of the last 10 NHL seasons with the Islanders, Flyers and six other teams, Robitaille has recorded 68 goals and 136 assists for 204 points and 161 penalty minutes in 413 regular season games.