Minimum Age for Sports Betting at a Casino Spinbetter is 21 years old. This applies to all forms of gambling, including betting online or in person. It is important to note that persons under the age of 21 are prohibited from placing any bets, no matter how small. Moreover, if someone is caught violating this rule, they may face serious legal consequences. So always make sure you are aware of the minimum age requirement before attempting to place a sports bet at a casino. Spinbetter.