Adolescent first‐time offenders demonstrate greater risk of continued offending, justice system contact, and high school dropout. The current study evaluates if optimistic expectations protect youth by reducing offending and improving school grades for 3 years following a first arrest (N = 1,165, Mage = 15.29). This article also considers whether improved behavior raises expectations about the future and uses autoregressive latent trajectory modeling with structured residuals to examine the within‐person cross‐lagged associations between expectations and behavior. The results indicated that positive expectations reduce offending and improve grades, which are in turn associated with higher expectations. Although raising expectations may improve outcomes following an arrest, ensuring adolescents have the tools to meet their goals may be an effective way to raise expectations.