Iraq–Kuwait relations evolved from hostility and mistrust toward institutionalized cooperation between 1990 and 2026. Drawing on Alexander Wendt’s “Three Cultures of Anarchy,” this study explains changes in bilateral relations and assesses the extent of their transition from Hobbesian to Lockean and Kantian cultures. It hypothesizes that this transformation resulted from interactions between changing mutual identities and norms and shifts in the regional material and structural environment. Accordingly, Lockean culture became dominant after 2003, while certain Kantian elements strengthened during the 2020s. The study employs a qualitative approach, descriptive–explanatory methodology, and historical-process analysis. Using process tracing, it examines changes in the definition of the “self” and the “other,” perceptions of interests and security, interaction rules, and behavioral patterns across three periods: 1990–2003, 2003–2022, and 2023–2026. Data from official documents, agreements, international resolutions, scholarly sources, historical records, and political evidence are assessed using operational indicators of the three cultures. Findings show that this transformation is neither linear nor irreversible; different cultures of anarchy may coexist across domains of bilateral relations. Contemporary Iraq–Kuwait relations are therefore predominantly Lockean, accompanied by growing Kantian elements. Persistent sovereignty and maritime disputes, particularly over Khor Abdullah, demonstrate that rivalry and national-interest considerations coexist with cooperation and self-restraint.