Purpose -Previous studies have shown that support workers often have difficulties in recognising mental health problems in service users with intellectual disabilities. In the context of improved UK training programmes, the purpose of this paper is to explore the factors that can predict support workers' knowledge and confidence in this respect. Design/methodology/approach -In total, 80 support workers (40 residential and 40 community-based) completed a questionnaire about their length of work experience, exposure to service users with additional mental health needs, training, general and specific mental health knowledge, and confidence in working with mental health issues. It was hypothesised that length of work experience, extent of training, and level of exposure would predict knowledge about mental health problems, and also predict confidence in working with people with mental health problems. It was further predicted that residential support workers would be more knowledgeable and confident than community workers. Findings -Results showed that level of exposure could predict knowledge about schizophrenia, but not about depression, anxiety, or dementia, while length of experience could predict overall mental health knowledge and confidence. Extent of training could only predict knowledge about anxiety, and work setting (residential or community) had no effect to on knowledge or confidence. Implications for practice and training are discussed. Originality/value -In the context of improved UK training programmes, this study aimed to explore the factors that can predict support workers' knowledge and confidence in this respect.