Mark Johnston, 52, says the Downtown Grand gave him $500,000 in casino markers and continued to serve him drinks while he was visibly intoxicated.
"Just picture a drunk man walking down the street - is it legal for somebody to walk up and reach into his pocket and take his money? No," said Johnston.
He thinks the casino should be held responsible for his big loss since Nevada law bars casinos from allowing obviously drunk customers to gamble.
The 52-year-old says he had drinks before, during, and after his flight to Las Vegas and even more at dinner.
"The airport, you know, getting on the plane, getting in the limo, going to Triple George's, I really don't remember anything after Triple George's," said Johnston, adding that he can't remember the next 44 hours.
In his lawsuit, Johnston says he lost the money playing blackjack and pai gow for 17 hours straight and had another 20 alcoholic drinks. During that stretch, the casino let him take out four lines of credit, totaling half-a-million dollars.
"Playing on credit is out of the ordinary for Mr. Johnston in the first place; drinking to the point of intoxication is out of the ordinary for Mr. Johnston" said his attorney Sean Lyttle.
Surveillance video will prove that he was blackout drunk, according to his legal team.
When he sobered up, Johnston says the casino told him he got a 20 percent discount and only owed $400,000 by March 31. He says the casino tried to collect the full debt after receiving a letter from his attorney.
The Downtown Grand says it does not comment on pending litigation. Johnston says he is willing to settle if it's a fair offer.
The Associated Press contributed to this report.