BACKGROUND: American youth are seriously impacted by depression and suicide. The Texas Youth Depression and Suicide Research Network (TX-YDSRN) Participant Registry Study was initiated in 2020 to develop predictive models for treatment outcomes in youth with depression and/or suicidality. This report presents the study rationale, design and baseline characteristics of the first 1000 participants. METHODS: TX-YDSRN consists of the Network Hub (coordinating center), 12 medical school "Nodes" (manage/implement study), each with 1-5 primary care, inpatient, and/or outpatient Sub-Sites (recruitment, data collection). Participants are 8-20-year-olds who receive treatment or screen positive for depression and/or suicidality. Baseline data include mood and suicidality symptoms, associated comorbidities, treatment history, services used, and social determinants of health. Subsequent assessments occur every two months for 24 months. RESULTS: Among 1000 participants, 68.7 % were 12-17 years, 24.6 % were ≥ 18 years, and 6.7 % were < 12. Overall, 36.8 % were non-Hispanic Caucasian, 73.4 % were female, and 79.9 % had a primary depressive disorder. Nearly half of the sample reported ≥1 suicide attempt, with rates similar in youth 12-17 years old (49.9 %) and those 18 years and older (45.5 %); 29.9 % of children <12 reported at least one suicide attempt. Depression and anxiety scores were in the moderate-severe range for all age groups (Patient Health Questionnaire for Adolescents [PHQ-A]: 12.9 ± 6.4; Generalized Anxiety Disorder [GAD-7]: 11.3 ± 5.9). LIMITATIONS: The sample includes youth who are receiving depression care at enrollment and may not be representative of non-diagnosed, non-treatment seeking youth. CONCLUSIONS: The TX-YDSRN is one of the largest prospective longitudinal cohort registries designed to develop predictive models for outcome trajectories based on disorder heterogeneity, social determinants of health, and treatment availability.