Objective: To evaluate the association between sleep characteristics and depressive and anxiety symptoms during the immediate postpartum period. Methods: People who had hospital births during 2019 in the municipality of Rio Grande (southern Brazil) were assessed with a standardized questionnaire concerning sociodemographic (eg, age and self-reported skin color) and health-related variables (eg, parity and stillbirth) (n = 2314) 24-48 hours after birth. We used the Munich Chronotype Questionnaire to assess sleep latency, inertia, duration, and chronotype; the Edinburgh Postpartum Depression Scale for depressive symptoms; and the General Anxiety Disorder 7-Item Scale to evaluate anxiety symptoms. We used logistic regression models to calculate odds ratios. Results: The prevalence of depressive symptoms was 13.7%, and of anxiety symptoms was 10.7%. Depressive symptoms were more likely in those with vespertine chronotype (odds ratios = 1.63; 95% CI: 1.14-2.35) and those with a sleep latency of more than 30 minutes (OR = 2.36; 95% CI: 1.68-3.32). The probability of depressive symptoms decreased by 16% for each additional hour of sleep (OR = 0.84; 95% CI: 0.77-0.92). Sleep inertia of 11-30 minutes increased the probability of anxiety on free days (OR = 1.73; 95% CI: 1.27-2.36) and increased the probability of depressive (OR = 2.68; 95% CI: 1.82-3.83) and anxiety symptoms (OR = 1.69; 95%CI: 1.16-2.44) on workdays. Conclusion: Participants with vespertine chronotype or shorter sleep duration were more likely to have depressive symptoms. Those who took more time to fall asleep or get out of bed were more likely to have both anxiety and depressive symptoms, but the association was stronger for depressive symptoms.