Purpose: We prospectively examined the influence of young women's depression and psychological stress symptoms on their weekly contraceptive method use. Methods: We examined data from 689 women ages 18-20 years participating in a longitudinal cohort study. Women completed 8,877 weekly journals over the first year, which assessed reproductive, relationship, and health information. We focused on baseline depression (Center for Epidemiologic Studies-Depression Scale) and stress (Perceived Stress Scale) symptoms and weekly contraceptive method use. Analyses used multivariate random effects and multinomial logistic regression. Results: Approximately one quarter of women exhibited moderate/severe depression (27%) and stress (25%) symptoms at baseline. Contraception was not used in 10% of weekly journals, whereas coital and noncoital methods were used in 42% and 48% of weeks, respectively. In adjusted models, women with moderate/severe stress symptoms had more than twice the odds of contraception nonuse than women without stress (odds ratio [OR] 2.23, confidence interval [CI] 1.02-4.89, p = .04). Additionally, women with moderate/severe depression (RR .52, CI .40-.68, p < .001) and stress (relative risk [RR] .75, CI .58-.96, p = .02) symptoms had lower relative risks of using long-acting methods than oral contraceptives (OCs; reference category). Women with stress symptoms also had higher relative risks of using condoms (RR 1.17, CI 1.00-1.34, p = .02) and withdrawal (RR 1.29, CI 1.10-1.51, p = .001) than OCs. The relative risk of dual versus single method use was also lower for women with stress symptoms. Conclusion: Women's psychological symptoms predicted their weekly contraceptive nonuse and use of less effective methods. Further research can determine the influence of dynamic psychological symptoms on contraceptive choices and failures over time. (C) 2013 Society for Adolescent Health and Medicine. All rights reserved.