Many consumers admitted to mental health inpatient units also use illicit drugs, and some continue to do so while receiving treatment. In an attempt to curb the impact of illicit drug use, one of Australia's largest mental health services introduced a programme of drug-detection dog (DDD) searches. Our aim was to evaluate perceptions of the DDD programme among mental health consumers, staff, and carers. A mixed-methods research design using a concurrent triangulation approach was adopted, involving three focus group discussions with consumer, staff, and carer groups, and a structured survey among 94 consumers who were receiving treatment and 102 staff working in the units at the time of a DDD visit. Data were analysed using thematic analysis, and descriptive and inferential statistics. Major themes were that: (i) drug use in these units is perceived as 'prevalent' and 'destructive'; (ii) the DDD programme is 'beneficial' but 'incongruous' in a health-care setting; (iii) consumers are 'uninformed'; and (iv) consequences should be 'customized' to circumstances. Survey results corroborated qualitative themes, with the exception that although concerns about incongruity do exist, they were not prevalent and were outweighed by positive perceptions of the programme. Most perceptions were consistent between consumers and staff. However, consumers tended to think that, if found, drugs should be confiscated, whereas staff were more strongly in favour of the consumer being discharged. In conclusion, the DDD programme was seen as a positive step towards addressing drug use in mental health units. However, improved dissemination of information to consumers through verbal and written communication is required.