Background: Transitional age youth (TAY) are a particularly at-risk population in mental health. They have specific needs, not currently covered between child and adolescent mental health services (CAMHS) and adult mental health services (AMHS), mainly because of existing barriers. This retrospective study was carried out to describe sociodemographic and clinical characteristics of patients who attended a new outpatient program specifically conceived for TAY in Brussels, Belgium. Outcomes related to trajectories of psychiatric care were analysed, such as leading symptom, consultation's referral and requester, and final orientation. Subjects and methods: The total sample included 243 patients aged from 16 to 24 years old who presented for care in this outpatient program between October 2019 and May 2021. Data were retrospectively extracted from each patient's electronic medical records. Results: The sample was mainly composed by female participants; the average age was 18.7 (±2.0) years. General practitioner (18.9%), child and adolescent psychiatrist (18.1%), psychologist (11.5%) and adult psychiatrist (7.4%) referred patients. Leading symptoms were divided into three dimensions: internalizing (67.5%), externalizing (21.8%) and psychotic (10.7%) ones. After first assessment, 81.5% of youth were followed-up in our specific outpatient program. Overall, at the end of data collection, youth were orientated towards ongoing follow-up in this program (37%), AMHS care (21.8%), end of psychiatric care (17.3%) and CAMHS care (4.1%). 19.8% patients discontinued the proposed care. Conclusions: This psychiatric outpatient program for TAY represents an innovative contribution to reinforce CAMHS-AMHS interface in French-speaking Belgium. The analysis of trajectories in psychiatric care suggests positive outcomes of this TAY-tailored clinical program to achieve high quality standard of care in youth mental health. Future research and clinical implementation programs should further explore which factors influence decision-making ...