The aim of this study was to explore knowledge use and learning among social workers in everyday child investigation work. Research was undertaken in two Swedish children’s services departments. The study applied an ethnographic approach. Methods for data collection included interviews, participant observations, reflective dialogues and a documentary analysis of case files. The social workers’ knowledge sources were classified into research-based, practice-based and ordinary knowledge. The findings show that the social workers preferred practice-based knowledge, which was primarily conveyed from colleagues and previous experience, and rarely consulted knowledge from sources found outside the practice setting. Furthermore, the findings suggest that the integration of knowledge was made possible through the social workers' engagement in both a verbal and a more cognitive (tacit) reasoning activity, processes that fostered learning at work. The social workers’ learning was predominantly adaptive as they learned to handle tasks in a fairly routinized way on the basis of rules or procedures. The findings lend support to the notion that the use of different knowledge forms could potentially trigger learning in everyday social work.