ABSTRACT Problem gambling in adolescence can lead to significant negative consequences, yet few studies have examined the prevalence and risk factors among diverse youth populations. This study investigated gambling and related non-gambling activities and sociodemographic correlates of problem gambling in 2,533 high-school students in New Mexico aged 12–18 years (mean age 15.6), with an approximately equal gender distribution (49.3% male, 49.3% female, 1.4% unspecified). Overall, 3% screened positive for problem gambling, with higher rates among males (3.9%) than females (2.1%), Native American (4.5%), and Hispanic (3.3%) versus white (1.5%) students. In-person activities were more common than online activities for both gambling and non-gambling activities. Substance use behaviors, including binge drinking, e-cigarette, marijuana, and prescription painkiller use, were more prevalent among people with gambling problems. Controlling for demographics, the interaction between Hispanic ethnicity and past 30-day binge drinking was positively associated with problem gambling. A risk score combining substance use and housing instability also positively predicted problem gambling. These findings demonstrate sociodemographic and substance use risk factors for problem gambling among New Mexico adolescents. The study highlights the importance of considering diverse ethnic backgrounds and co-occurring risk behaviors in developing targeted prevention and intervention strategies for adolescent problem gambling across various cultural contexts.