Background: Differences in sexual health-related outcomes by sexual behavior and identity remain underinvestigated among bisexual female adolescents. Methods: Data from girls (N?=?875) who participated in the Massachusetts Youth Risk Behavior Surveillance survey were analyzed. Weighted logistic regression models were fit to examine sexual and psychosocial health by lifetime sexual behavior (behaviorally bisexual vs behaviorally heterosexual) and sexual identity (bisexual vs heterosexual) adjusting for grade and race/ethnicity. Results: Overall, 10.5% of girls reported lifetime bisexual behavior and 8.1% reported a bisexual identity. Behavior and identity were discordant for bisexual young women as 53.2% of behaviorally bisexual students had a bisexual identity and 46.8% had a heterosexual identity. Bisexual identity and behavior were associated with unprotected intercourse at last sexual encounter, early sexual debut, 4 or more lifetime partners, history of forced/unwanted sex, sexually transmitted infection testing history, past-year depression, and past-month drug use (all ps?<0?.05). Conclusion: Bisexuality, whether defined by identity or behavior, is associated with adverse sexual and psychosocial health outcomes in adolescent girls. Studies that explore wellness across the life span, and are designed to recognize developmental differences burgeoning in adolescence, may provide insights into the differential sexual risk outcomes observed among bisexual girls.