Background Working with victims and perpetrators of child sexual abuse has been shown to cause secondary traumatic stress (STS) in child protection professionals. Aims To examine the role of gender and personality on the development of secondary trauma responses. Methods A study of Internet child abuse investigators (ICAIs) from two UK police forces. Participants completed a personality test together with tests for anxiety, depression, burnout, STS and post-traumatic stress disorder to assess secondary trauma. The data were normally distributed and the results were analysed using an independent t-test, Pearson correlation and linear regression. Results Among 126 study subjects (50 females and 75 males), there was a higher incidence of STS in investigators who were female, introverted and neurotic. However, there were lower levels of STS in the participants in this study than those found in other studies. Conclusions Psychological screening and surveillance of ICAI teams can help to identify risk factors for the development of STS and identify where additional support may be required.