Purpose <p>Existing classifications of housing instability often oversimplify the diverse experiences of unstable housing among youth, potentially obscuring varied health risks. This study addresses this gap by examining the nuanced classification of housing instability and its association with behavioral health outcomes among U.S. high school students.</p> Methods <p>Data from the 2021 and 2023 Youth Risk Behavior Surveys (<i>n</i> = 26,219) were utilized. Housing status was categorized into four levels: housing stability, uncertain housing stability, housing instability, and severe housing instability. Outcomes included alcohol, cannabis, and tobacco use, and mental health-related outcomes (persistent sadness, suicidal thoughts, and suicide attempts). Multivariable logistic regressions were employed to examine these associations.</p> Results <p>Compared to stably housed peers, students experiencing any form of housing instability had significantly higher odds of substance use and mental health-related issues. A clear dose-response association emerged: higher odds of substance use, suicidal thoughts, and suicide attempts were associated with more severe housing instability. Specifically, those with severe housing instability had considerably elevated odds for alcohol use (OR = 4.99, 95% CI [2.94, 8.48]), cannabis use (OR = 3.88, 95% CI [2.23, 6.76]), tobacco use (OR = 7.31, 95% CI [5.15, 10.38]), suicidal thoughts (OR = 3.53, 95% CI [2.28, 5.47]), and suicide attempts (OR = 8.38, 95% CI [5.68, 12.38]).</p> Conclusion <p>Housing instability, particularly its more severe forms, is strongly associated with a higher likelihood of substance use and suicidality among U.S. high school students. This classification highlights distinct potential behavioral health risks associated with various indicators of housing instability.</p>