The purpose of this study was to investigate whether clinicians investigating child sexual abuse (CSA) rely more on scientific knowledge or on clinical experience when evaluating their own expertise. Another goal was to check what kind of pre-trial beliefs the clinicians had. The connections between these different factors were investigated. A questionnaire covering items concerning demographic data, experience, knowledge about CSA, self-evaluated expertise and beliefs about CSA was given to 126 social workers, 60 child psychiatrists and 134 psychologists. The results showed that the clinicians relied more on their clinical experience than on scientific knowledge when evaluating their expertise as investigators of CSA. Furthermore, social workers possessed stronger attitudes in favor of children than the other groups, while child psychiatrists had more negative attitudes towards the criminal justice system. Male participants had less strong beliefs than did the female participants. The findings indicate that the education of CSA investigators should focus more on theoretical knowledge and decision-making processes as well as the role of pre-trial beliefs.