The aim of this study is to describe and analyze how social workers experiences internal collaboration within child and welfare social services and how social workers describe the forms of internal collaboration in their practical work. The study is based on seven semi-structured interviews in seven municipalities with social workers, from three units within child and welfare social services. The collected empirical material were analyzed with theoretical concept discretion, cooperation theory and former research. The results of the study shows that social workers primarily have a positive attitude towards internal collaboration, due to the fact that clients with complex problems are in need of support from various social workers from different units. Furthermore the study found that social workers ordinarily use two different methods when collaborating: informal collaboration and formalized collaboration. Moreover social workers express a variety of obstacles in collabortation with other untis, such as lack of knowledge about each other´s duties, confidentiality and lack of time. It also shows that geographical nearness, good relationships and knowledge are important components for serviceable collaboration. Finally, the study results shows that internal cooperation in child and welfare social services is a necessary working method in order for social workers to be able to meet the needs of clients with complex problems.