The Russia-Ukraine conflict has triggered an unprecedented wave of unilateral sanctions by Ukraine and its allies, significantly impacting businesses run by investors that are directly or indirectly affected by these measures. In response, investors are turning to international investment agreements (IIAs) to seek compensation for losses. This article examines the ratione personae issues that may arise in sanctions-based investment disputes, including whether holding the home state’s nationality alone is sufficient for protected investor status, or whether tribunals should look to the corporate claimant’s shareholders to determine its nationality. It also proposes treaty reforms that states can adopt to clarify and resolve the challenges posed by nationality requirements in the context of such disputes.