The entry into force of the Treaty on the Prohibition of Nuclear Weapons (TPNW) in January 2021 has sparked much discussion of the Treaty's positive obligations under Article 6. But while victim assistance under Article 6(1) has received considerable attention, the environmental remediation obligation within Article 6(2) remains underexplored. Filling this gap, this article examines a specific issue relating to environmental remediation under Article 6(2): the scope of nuclear weapons-related activities captured by the obligation imposed upon TPNW parties. Ultimately, it is revealed that significant ambiguity exists as to the scope of activities covered when applying the rules of treaty interpretation of the 1969 Vienna Convention on the Law of Treaties. After offering some policy arguments both for and against a broad interpretation, this paper recommends that TPNW parties should begin to advance and clarify their positions on this issue in order to clearly identify the scope of Article 6(2).