Summary Given the global and local social inequalities and the complex life circumstances of people living in poverty, social workers are called upon to broaden their knowledge with the purpose of developing social services that respond to the needs of this growing population. However, very little research has been done on the kind of knowledge that social workers require in order to care for this population. The present article focuses on the epistemological aspects of service development for people living in poverty and reviews three main issues: What is “poverty knowledge,” where does it come from, and what are the barriers to and opportunities for its development? These questions are investigated through a qualitative paradigm among social workers employed in Israel’s public social services. Findings Findings reveal a profound epistemological controversy about what poverty knowledge means: Is it objective, consistent, readily available, and transferrable knowledge, or is it a dynamic and reflexive process affected by a great number of fluctuating contexts? Findings stress the dominance of positivist views of poverty knowledge, mostly derived from practice while other sources of knowledge development, such as service users’ local knowledge, theory, and research knowledge were seen as less relevant to their needs. Applications Practical recommendations are offered relating to the need for poverty knowledge development processes in social services as well as in social-work education through collaborative, contextual, and reflective learning with and from service users and other stakeholders.