David Hart, 23, who was from Poppleton, near York, England, took out a $500,000 life insurance policy before going to Afghanistan, The Sun reported Monday.
In addition to the Las Vegas money for his friends, he left part of the insurance money to a charity for insured marines.
He wrote a letter saying he wanted to send his friends and their girlfriends to Las Vegas to party in his memory if he died.
Hart, a combat medic, was killed a year ago in Helmand province, an area with much Taliban activity, in Afghanistan.
"He loved going away with his mates -- it was always the best two weeks of the year," said friend Andy Hare, 25. "They were lads' holidays and great times."
Thirty-two of Hart's 'lads' will be taking the trip, including Hare, a construction manager.
"In his letter, David said he had had a great life and had no regrets about anything. He always said he would do something like this if something bad happened. He said, 'Go and have a good time and spend all this money,'" Hare said.
After Hart's death, Lt. Col. Paul James described him as "the perfect marine -- magnificent in personality and profession."