In Germany (and other countries) a significant proportion of children and young people in contact with the child welfare system do not receive adequate mental health care. Fragmented service delivery has been partially attributed to a lack of interprofessional collaboration between the child welfare system and providers of child mental health services. Child and adolescent psychiatric (CAP) clinics provide the majority of child mental health care for the child welfare population in Germany. In this paper, we present the first wave of data collected in a nonrandomized pretest–posttest intervention study, in which we examined the collaboration between child welfare services and CAP clinics in Northern Germany with a sample of N = 204 professionals in total, from both organizations. We used two standardized measurements. The general quality of collaboration was measured using an established tool, the “Perceptions of Interprofessional Collaboration Model – Questionnaire” (PINCOM-Q). Perceptions of collaboration around children with complex care needs were measured with a newly developed scale, the “Perceptions of Interprofessional Collaboration Scale for Children with Multiple and Complex Needs” (PICOCC). The results show that perceptions of interprofessional collaboration differed based on organizational and professional affiliation. Frontline workers employed in the child welfare system compared to those working in CAP clinics had a more negative perception of collaboration in general, and felt their organization provided less support for collaboration. Social workers in both CAP and child welfare services perceived less organizational support for collaboration compared to mental health professionals. In the overall group of social workers, those working in the child welfare system felt their organization supported collaboration the least. Mental health professionals working in CAP clinics, however, had a more negative perception of collaboration around children with complex needs. This suggests that attention should be paid to perceptions of interprofessional collaboration as an important process variable, which may impact on frontline workers’ responsiveness to organizational change.