This document provides an overview of systems theory as it relates to social work. It defines systems theory as examining how individuals, groups, organizations, and communities interact as interconnected parts of a whole. It discusses key concepts in systems theory including boundaries, interactions, feedback loops, and homeostasis. Examples are given of how systems theory can be applied to understand issues like school refusal from an ecological perspective considering the interactions between family members and other systems. The strengths of systems theory are that it takes a holistic view and allows for an eclectic approach, while weaknesses include a lack of specificity and potentially overemphasizing stability over change.