Purpose: Headspace services provide treatment options to young people seeking mental healthcare. To obtain a better understanding of needs and characteristics of this population, and effectively evaluate services, we require novel youth-specific outcome measures. As part of our broad research program to establish such measures, a sample of young people were recruited and assessed. The study describes (i) methodology used to obtain clinical, functioning, and substance use characteristics of young people presenting to headspace services; and (ii) an overview of these characteristics. Methods: Young people presenting to headspace centres were recruited. Multidimensional information was obtained relating to clinical and functional outcomes, demographic information, and lifestyle factors. Results: 1107 young help-seeking individuals were recruited. Participants were most likely young adults aged M = 18.1 years, SD = 3.3, with diagnoses of depression and/or anxiety (76.6%, n = 801), engaged in work and study (84.9%, n = 890), and living with parent(s) (68.9%, n = 736). Impairments in functioning were moderate as indicated by the Social and Occupational Functioning Assessment Scale (M = 65.2, SD = 9.5), substance use was common (alcohol 62.7%, n = 665; illicit substances 30.5%, n = 324), and current suicidal ideation was reported by a third (33.6%, n = 358). Conclusions: A broad dataset was obtained providing an insight into key clinical, functional and quality of life characteristics of these individuals. We observed that young people present with complex problems, comorbid diagnoses, moderate levels of symptomatology, impairments in functioning, substance use, and suicidal ideation. This work provides the foundation for our broader research program aiming to develop novel, relevant and youth-specific, change and outcome measures.