Background: We prospectively followed an ethnically and socioeconomically diverse sample of girls with attention-deficit/hyperactivity disorder (ADHD) (n = 140) and a matched comparison sample (n = 88) from childhood through young adulthood to evaluate developmental trajectories of executive functions (EF) and associations between EF trajectories and dimensional measures of ADHD symptoms. We hypothesized that (a) EF trajectories would be similar in girls both with and without childhood ADHD, with the ADHD group showing greater impairment across time; and (b) changes in EF abilities would predict changes in ADHD symptoms across time, consistent with the theory that ADHD symptom reductions partially result from prefrontally mediated EF development. Method: Latent growth curve models were used to evaluate development of sustained attention, response inhibition, working memory, and global EF abilities, and associations between EF trajectories and ADHD symptom trajectories. Results: Girls with childhood-diagnosed ADHD showed greater improvement across development on measures of sustained attention and global EF, but similar rates of improvement on measures of working memory and response inhibition. Changes in the global EF measure predicted changes in both inattentive and hyperactive-impulsive symptoms across time, whereas changes in response inhibition predicted changes in hyperactive-impulsive symptoms; associations between changes in other EF variables and symptoms were not significant. Conclusions: Findings suggest variability in patterns of EF improvement over time in females with ADHD histories and indicate that EF development may play a role in symptom change.