18+ or 21+ There are two distinct legal ages when it comes to casino gambling in the US, and it depends on your jurisdiction. In some states, the legal age to go to a casino is 18 and up, while in others it’s 21 and up. Often, the distinction has to do with whether or not the venue in question serves alcohol. All that said, the best online casinos for US players set their membership age minimums to just 18+. Please never sign up at an offshore gambling site under the age of 18, as this will lead to your account being banned and your funds being forfeited.