With the popularity of Internet use among adolescents, there is concern that some youth may display problematic or addictive patterns of Internet use. Although excessive patterns of Internet use was considered for inclusion in the DSM-5 with pathological gambling and substance-use disorders in a category of addictive disorders, it was determined that more research was needed on Internet-use behaviors before such actions be further considered and possibly undertaken. The present study is the first to investigate whether at-risk/problematic Internet use (ARPIU) may moderate the strength of association between problem-gambling severity and gambling-related characteristics and health and well-being measures in adolescents. Survey data from 1884 Connecticut high-school student stratified by Internet use (ARPIU vs. non-ARPIU) were examined in bivariate analyses and logistic regression models. Gambling-related characteristics and health and well-being measures were mostly positively associated with problem-gambling severity in both Internet use groups. Interaction odds ratio revealed that the strength of the associations between problem-gambling severity and marijuana, alcohol and caffeine use were stronger amongst the non-ARPIU compared to the ARPIU group, suggesting that the relationships between these substance use behaviors and problem gambling may be partially accounted for by ARPIU. Future studies should examine the extent to which preventative interventions targeting both problematic Internet use and problem gambling may synergistically benefit measures of health and reduce risk-taking behaviors in adolescence.