Objective The aim of this study was to review animal hoarding cases referred to the Royal Society for the Prevention of Cruelty to Animals (RSPCA) in New South Wales (NSW) to examine mental health factors that influence the development of animal hoarding and to consider strategies for dealing with such cases. Methods Data were gathered by RSPCA inspectors regarding consecutive cases referred to the agency over 2 years. Result Details were provided about animals and 50 identified hoarders (11 male, 39 female; mean age 57 years) on 48 properties. The mean number of animals per case was 53 (range 6-300). Fifteen participants (30%) were known to have had involvement with mental health or social services. Mental health factors appeared to contribute to animal hoarding in well over 50% of cases. Severe and moderate squalor were observed in 52% and 21% of dwellings assessed respectively, many with accumulated rubbish. Conclusions Animal hoarding is largely attributable to psychological and psychiatric problems. It is recommended that clinical services work alongside animal welfare inspectorates, assessing (and, where appropriate, treating) such problems. What is known about the topic? Animal hoarding is believed to be partly attributable to the hoarders having psychiatric or psychological problems, but relevant mental health assessment of hoarders is not usually arranged. Recidivism after removal of animals is nearly 100%. What does this paper add? The study confirms that animal hoarders commonly have mental health issues. However, RSPCA inspectors are not expected to screen for such issues or refer cases to mental health clinicians. What are the implications for practitioners? There is good reason to develop clinical services to help animal hoarders deal with their psychological or psychiatric problems.