The casinos themselves can get into legal trouble if they allow someone who is underaged to gamble. It doesn’t matter if you’re with an adult. Even if you’re not gambling, casinos will kick you out for merely standing near slot machines or table games. The same rules apply to underaged patrons hanging out on the casino floor. At the bare minimum, you will be kicked out and banned from the casino. If you’re underaged and get caught gambling, you can be charged with a misdemeanor and spend time in jail. It’s not just an arbitrary rule that casinos have, it’s a real criminal offense for someone under the age of 21 to gamble in Las Vegas. This applies to all forms of gambling, including slot machines, table games, sports betting, poker, horse racing, and bingo. You must be 21 years old AND have a valid ID to gamble in Las Vegas casinos. However, Nevada is not one of those states. Some states allow you to gamble if you’re at least 18 years old. How Old do You Have to be to Gamble in Vegas?