The focus of this thesis is on social workers’ knowledge in assessing and making decisions in child welfare cases. The primary aim is to identify what skills or knowledge social workers find most useful within child welfare agencies in Swedish municipalities. Six different types of knowledge, social policy and the approach of child welfare cases are perspectives considered in the analysis. The interviews with social workers were held in three agencies in southern Sweden, in 2014. Main results: social workers’ think it is very important to have different kinds of knowledge and skills in order to perform such professional work as possible. They value peer support where they can exchange experiences and knowledge with each other. The importance to specialize after the bachelor’s degree in social work was also revealed in the results, due to the social work supplementary course only represented undergraduate studies. The approach of child welfare cases it was found that there are many different ways to manage them, but the main thing is to manage the cases with great respect and always strive to apply volunteer efforts where it’s possible. Another point is the political importance which we not counted on.