Background: Adolescent substance use is often associated with concurrent mental health problems (e.g., depression, suicide attempts, parental emotional and physical abuse, not feeling close to people at school, and lower virtual connectedness) at multiple ecological levels. Objective: This study examined whether such risk factors among adolescents were associated with the use of telemental healthcare (TMHC) and whether gender moderated these associations. Methods: Data were drawn from the Adolescent Behaviors and Experiences Survey, collected by the U.S. Centers for Disease Control and Prevention from January to June 2021. A hierarchical multiple logistic regression analysis was conducted using a national sample of 1,460 students in Grades 9-12 in the United States who reported having used more alcohol and/or drugs during the pandemic than before it started. Results: The results showed that only 15.3% of students sought TMHC. Students reporting increased substance use during the pandemic were more likely to use TMHC if they experienced more severe mental health problems (e.g., suicide attempts) compared to other ecological factors, such as issues with their family, school, or community. Analysis of the moderating effect showed that the closer male students felt to people at school, the more likely they were to seek TMHC, whereas the opposite was true for female students. Conclusions: The findings highlighted that feeling close to people at school is an important aspect of understanding the help-seeking behavior of female and male adolescent substance users.