Mental health is increasingly viewed as a complete state of being, consisting of the absence of psychopathology and the presence of positive factors such as subjective well-being (SWB). This cross-sectional study analyzed multimethod and multisource data for 500 high school students (ages 14-18 years, M = 15.27 years, SD = 1.0 years) to examine how mental health, defined in a dual-factor model, relates to adjustment. Relevant outcomes within self-determination theory include academic adjustment, social adjustment, identity development, and physical health. A dual-factor model was supported through identification of four groups: complete mental health (62.2% of sample), vulnerable (11.4%), symptomatic but content (11.4%), and troubled (15%). Results extend the importance of high SWB to optimal functioning during middle adolescence, as students with complete mental health (high SWB, low psychopathology) reported better outcomes than vulnerable students (low SWB despite low psychopathology) in terms of academic attitudes, perceptions of overall physical health, social support and satisfaction with romantic relationships, and identity development. Among students with elevated psychopathology, those with high SWB (symptomatic-but-content group) reported greater academic self-perceptions, perceived physical health, social support and satisfaction with romantic relationships (as well as less peer victimization), and identity development than their peers with low SWB (troubled group). Main effects of SWB in multilevel models that controlled for psychopathology and demographic covariates further illustrate the additive value of SWB in mental health assessments in terms of explaining unique variance in student adjustment in all four domains examined.