In Chile, Law 21.057 established in 2019 that, for criminal cases in which there is a child or adolescent victim of a sexual or other serious crime, professionals who take the evidence from the victim during the investigative interview and court testimony are required to be specially trained as interviewers and intermediaries, respectively. Although Chile has been progressively moving into a child-friendly justice system, the expertise and training on how to address victims who have particular communicative, emotional, cultural, or social needs have been rather limited. This study explores the challenges experienced by investigative interviewers and intermediaries with child victims from priority groups, through the lens of their instructors. The term “priority groups” encompasses people who require special protection because of a condition that puts them at a disadvantage. Using purposive sampling, 12 of the most experienced instructors were recruited, and five semi-structured group interviews were conducted remotely. Through thematic data analysis, eight categories of challenges were found. First, the study identified particular difficulties experienced by professionals with six groups of children and adolescents who are here called priority victims or members of priority groups: (1.1) preschool children, (1.2) victims with neurodevelopmental disorders, (1.3) victims with psychiatric disorders, (1.4) reluctant victims, (1.5) Indigenous and migrant victims, and (1.6) victims in complex contexts/crimes. Secondly, the analysis identified cross-cutting challenges for the professionals related to (2.1) difficulties remaining after their initial training, and (2.2) the unavailability of background information about the victims before the proceedings. The article emphasizes the need to strengthen advanced competences and training content regarding priority groups, to reinforce initial skills, and to refine guidelines to assess and address these victims adequately, in order to facilitate their access to justice.