BACKGROUND: This study evaluates a mobile phone self monitoring tool designed to assist paediatricians in assessing and managing youth mental health. METHODS: Patients from an adolescent outpatient clinic monitored mental health symptoms throughout each day for 2-4 weeks. Paediatricians specialising in adolescent health and participants reviewed the collated data displayed online and completed quantitative and qualitative feedback. RESULTS: Forty-seven adolescents and six paediatricians participated. Completion was high, with 91% of entries completed in the first week. Paediatricians found the program helpful for 92% of the participants and understood 88% of their patients' functioning better. Participants reported the data reflected their actual experiences (88%) and was accurate (85%), helpful (65%) and assisted their paediatrician to understand them better (77%). Qualitative results supported these findings. DISCUSSION: Self monitoring facilitates communication of mental health issues between these paediatricians and patients and is a promising tool for the assessment and management of mental health problems in young people.