This paper considers historical, legal and technical bases for including “control” of nuclear material as part of a State’s system of accounting for and control of nuclear material (SSAC) and its role in the fulfillment of safeguards obligations. Nuclear material control is a set of technical and administrative measures that a regulatory body and operators engage in to ensure that nuclear material is not misused or removed from its assigned location without proper authorization and accounting. Each non-nuclear-weapon State party to the Treaty on the Non-Proliferation of Nuclear Weapons (NPT) is required to conclude a safeguards agreement with the International Atomic Energy Agency (IAEA); this is done based on Information Circular 153. During the negotiation of the text of INFCIRC/153 in the early 1970s, States considered proposals for including specific requirements for the control of nuclear material but these proposals were ultimately rejected on the basis that the monitoring of such “physical security” measures was not within the IAEA’s safeguards mandate. Instead, each safeguards agreement relies on the State maintaining its SSAC and the IAEA applying predominantly accountancy measures to verify findings of the State’s system, including that nuclear material has not been removed from its declared location or misused. The IAEA’s safeguards guidance documents have recognized that measures taken by the State to control nuclear material remain crucial to effective safeguards implementation. Over time, the IAEA has also developed guidance in the field of nuclear security, which came to encompass nuclear material control. Although issued by the IAEA under the heading of security (and separately from the IAEA’s recommendations in the field of safeguards), recent publications on control in the Agency’s Nuclear Security Series are directly relevant to assisting States to meet their safeguards commitments effectively. Notwithstanding the dichotomy between nuclear safeguards and nuclear security in the IAEA’s guidance documents and its departmental structure, nuclear material control represents a shared set of tools for supporting States’ implementation of both safeguards and security. Practitioners in safeguards and security should be aware of this confluence and be able to manage potential areas of conflict.