To investigate the prospective association of diet pill and laxative use for weight control with subsequent first eating disorder diagnosis in young women. We used longitudinal data from 10 058 US women spanning 2001 through 2016. We used multivariable logistic regression models, adjusting for age, race/ethnicity, and overweight status to estimate the association between weight-control behaviors and subsequent eating disorder diagnosis. Among those who had not previously received an eating disorder diagnosis, women who reported diet pill (adjusted odds ratio [AOR] = 5.6; 95% confidence interval [CI] = 3.0, 10.5) or laxative (AOR = 6.0; 95% CI = 4.2, 8.7) use for weight control had higher odds of receiving a subsequent first eating disorder diagnosis within 1 to 3 years than those who did not report using these products. Use of diet pills or laxatives for weight loss can be dangerous and may be a warning sign that warrants counseling and evaluation for the presence of or risk of developing an eating disorder. Policymakers and public health professionals should develop and evaluate policy initiatives to reduce or prohibit access to diet pills and laxatives abused for weight control.