Objective: To examine 5-year longitudinal and secular trends in weight-related teasing among adolescents. Methods and Procedures: Project EAT-II (Eating Among Teens-II) followed 2,516 adolescents (females = 1,386, 55.1%) prospectively from 1999 to 2004. EAT-II included two cohorts allowing the observation of longitudinal changes in reported weight-related teasing as participants transitioned from early to mid-adolescence (middle school to high school) and from mid- to late-adolescence (high school to post-high school). EAT-II also allowed the examination of secular trends in reported teasing among middle adolescents in 1999 and 2004. Results: In 1999, approximately one-quarter of adolescents in the total sample (including both overweight and nonoverweight youth) reported being teased about their weight in early adolescence and mid-adolescence. Prevalence rates of teasing were higher among overweight youth (early adolescence: females 42.4%, males 44.6%; mid-adolescence: females 31.2%, males 40.8%). Longitudinal trends suggest that weight-related teasing decreased among overweight males and females in the younger cohort as they transitioned from early adolescence to mid-adolescence. In the older cohort of youth, teasing decreased in the total sample of females as they transitioned from mid-adolescence to older adolescence. Analyses of age-matched secular trends among middle adolescents showed that the prevalence of weight-related teasing remained stable among most adolescent subgroups and declined among overweight males between 1999 and 2004. Discussion: Weight-related teasing is prevalent through the various stages of adolescence. Our findings point to a need for ongoing interventions, throughout adolescence, which focus on reducing weight-related teasing and improving social supports for affected youth.