Objective: Public stigma against mental illness is well studied. However, there is a dearth of research into health workers' attitude towards children and adolescents with mental illness, especially in low- and middle income countries such Nigeria. Methods: A cross-sectional study was conducted among 395 health workers in a Teaching Hospital in North-Central Nigeria. Participants were selected by random sampling from clinical and non-clinical departments. Participants completed questionnaires to assess stigma, knowledge, personal contact, previous training, and exposure to religious teaching on child and adolescent mental illness (CAMI). Results: The response rate was 90%. Many health workers (42%) indicated that affected children should not play with other children, 38% would feel ashamed if a child in their family had mental illness, 42% would be concerned if their child sat with an affected child, and 27% would be afraid to speak to a child or adolescent with mental illness. Independent predictors of negative attitudes were: poor knowledge, exposure to religious teaching that affected children are possessed or dangerous, and being from a non-medical professional group. Conclusion: CAMI is stigmatised by health workers in this specialist Hospital in Nigeria. Urgent intervention is required to avoid adverse impact on affected children.