The 38-year-old, a multiple La Liga and Champions League winner with Real Madrid, played the full game, setting up third goal of Gaston Cellerino's hat-trick with a delicate flick.
The Cosmos claimed their second North American Soccer League Soccer Bowl title, to go with the one they captured in 2013.
"I"m very happy," said Raul.
"It was my last game in my career.
Raul ready to hang his boots in November
"I'm very proud for everything I did and thank you to the club, my teammates and the fans for this amazing year.
“For me now, I start a new life with another project. I'm happy, but I'm also very sad."
While Raul was the man of the moment, Cellerino was the man of the match, which also sent Spain's Marcos Senna into retirement a winner.
"To win next to Raul was an ideal situation," said Senna.
"I'm thankful for him being here throughout the year as he made the difference many times and scored many goals.
"Today he didn't get the goal, but he got the assist. He's a player that is a game-changer."
Raul began his pro career at Real Madrid in 1994 and spent 16 years with the Spanish side, sparking the capital side to six La Liga crowns, four Spanish Super Cups and three UEFA Champions League titles.
He departed in 2010 as Real Madrid's all-time top goal scorer with 323, before recently being equalled by Cristiano Ronaldo on September 30.
After netting 40 goals in 98 matches for Germany's Schalke 04 and helping the Bundesliga side to the 2011 Champions League semi-finals, he departed in 2012 for Qatari side Al-Sadd and retired in 2014 only to make a comeback late last year with the Cosmos.
The club's appreciation was evident as Cosmos players lifted Raul and Senna into the air in a post-game tribute.
"We feel very lucky, our organization, to have these two great players retire with us," head coach Giovanni Savarese said.
"These two great players I had the pleasure to coach makes a coach's life easier because of the quality when they play.
“They were very important all year to push everybody to higher standards. The way they finished their careers today couldn't be any other way."
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