There are a number of reasons why the legal age to gamble in Nevada is 21. And, the legal age to gamble in the state’s Indian casinos is 18 or older, depending on the tribe’s regulations. The legal age to gamble at horseracing tracks in Nevada is 18. This applies to all forms of gambling, including casinos, lotteries, and online gambling. In the state of Nevada, the legal age to gamble is 21.