This study examined the influence of stigma, psychopathology, and sociodemographic characteristics on mental health-related service use and costs related to service use in a cohort of young people in the UK. Using data from a community sample of young people aged 9–17 years and their caregivers, we assessed 407 young people’s use of services due to mental health problems, young people’s psychopathology, demographic characteristics, maternal education and caregivers’ stigma-related beliefs. Unit costs related to services were gathered from national annual compendia and other widely used sources. We assessed predictors of service use through logistic regression analysis and developed generalised linear models to identify factors associated with costs of mental health-related service utilisation. Persistent psychopathology, socioeconomic disadvantage, and low caregiver intended stigma-related behaviour were associated with increased likelihood of service use among young people. Older age and socioeconomic disadvantage were associated with increased costs. Different factors influenced contact with services and the cost associated with their use — persistent psychopathology and socioeconomic disadvantage increased, and caregivers’ intended stigma-related behaviour decreased the likelihood of using services, whereas socioeconomic disadvantage and older age were associated with increased costs. Social determinants of mental health problems play an important role in the use and costs of different types of mental health-related services for young people. Discordance between drivers of service use and costs implies that young people who are more likely to access services due to mental health problems do not necessarily receive care at the intensity they need.