A dual-factor model of mental health includes indicators of wellness (i.e., subjective well-being; SWB) and psychopathology (i.e., internalizing and externalizing behavior problems) in defining youth mental health. In this model, four categories of psychological functioning with distinct levels of SWB and psychopathology emerge, including two that are overlooked (i.e., Vulnerable and Symptomatic but Content) in traditional assessments that assume SWB and psychopathology are opposite ends of the same continuum. The present study investigated the 1-year stability of adolescent mental health as classified by a dual-factor model, and identified predictors of stability and change, in a sample of 425 high school students. Results included that 60% of the high school students remained in the same mental health group over both time points. The Complete Mental Health Group (i.e., high SWB and low psychopathology) showed the most stability over time as nearly 80% of students initially in this group retained that mental health profile one year later. The initially Symptomatic but Content group (i.e., high SWB and high psychopathology) showed the least stability, with only 17% of students remaining in this mental health group the following year. Higher socioeconomic status and lower neuroticism reliably and uniquely predicted which students who initially experienced Complete Mental Health remained that way. Low neuroticism also predicted which students with partial mental health initially (i.e., Vulnerable or Symptomatic but Content) improved to Complete Mental Health. Once the shared variance amongst factors had been accounted for, no factors reliably and uniquely predicted which students initially Troubled stayed that way, nor which students moved from partial mental health (i.e., Vulnerable, Symptomatic but Content) to Troubled. This study contributes to the literature by providing the first examination of the stability of high school students' mental health as defined by a dual-factor model. Additionally, this study provides insight into the factors which predict students' stability and movement across mental health groups over time. Both sets of findings can be useful for school-based mental health professionals' prevention and intervention work with regard to how to operationalize student mental health, and intrapersonal risk factors important to detect.