Recently there has been an increase in so-called ‘radicalization cases’, cases that are centered around the possible impact of an extremist ideology of parents on their children, and that ask for a decision on whether child protection measures are needed to prevent children from harm. However, there is a lack of knowledge on the potential harmful effects of growing up with parents who adhere to a specific ideology. Consequently, judges and Child Protection Agencies involved in radicalization cases need to make decisions without much guidance or solid evidence. This study offers an initial exploration based on the analysis of Dutch published case law (n = 37) within the framework of international human rights law, Dutch legislation and available literature to assess when judges consider extremist and strict religious beliefs of parents harmful to their child. The results of the study indicate that judges in these cases take several factors into consideration when deciding whether a child protection measure, and if so, which one is necessary. These factors are the well-being (physical, social or emotional) of the child and the home situation. Our findings show that it follows from the case law that Dutch judges do not consider solely the beliefs of parents to pose a developmental threat (i.e., harm) to the child. Case law rather showed that it were the concrete actions of parents resulting from their beliefs that may constitute harm. Such actions can be traveling to Syria to join IS, keeping children from school, and denying medical treatment. The approach as taken by national courts therewith appears to be in line with international human rights standards.