The overarching argument of this thesis is that, contemporary international criminal courts and tribunals have, to varying degrees, exerted significant impacts on judicial, legislative, and executive, thoughts, processes, and actions within conflict, post-conflict and non-conflict states in the Commonwealth. This thesis analyzes evidence of these impacts by examining states in the Commonwealth, where contemporary international criminal courts and tribunals have operational and jurisdictional relevance. It does this by categorizing such states into four groups of states, conflict, post-conflict, non-conflict states and states where contemporary international criminal courts and tribunals have made marginal impacts. The thesis evaluates the impacts of contemporary international criminal courts and tribunals in these states by analyzing evidence, garnered from a study of judicial, legislative and executive actions and processes influenced directly or indirectly by contemporary international criminal courts and tribunals with operational and jurisdictional relevance in the Commonwealth. The thesis also undertakes an assessment of the overall impact of contemporary international criminal courts and tribunals in the Commonwealth on judicial, legislative and executive thoughts, actions and processes. In assessing the impact, the thesis is framed by two overarching arguments which set the tone for the discussions and analysis undertaken here. The first is that, certain factors such as engagement by the different courts and tribunals with states, the role of states actors and institutions; have helped contemporary international criminal courts and tribunals exert marginal to major influences on judicial, legislative and executive thoughts, processes and actions within the Commonwealth. The second overarching argument made in the thesis in assessing the impact of these contemporary international criminal courts and tribunals is that, certain factors such as the poor visibility of international criminal courts and tribunals within Commonwealth States, conflicting visions of justice that these courts and tribunals ought to dispense by relevant stakeholders and the non-transposition of the norms of international criminal law and international humanitarian law within Commonwealth States; have inhibited the impact of these courts and tribunals on judicial, legislative and executive thoughts, processes and actions within the Commonwealth. It concludes by noting that international criminal courts and tribunals have had different levels of impacts on states across the Commonwealth due to the coalescence of the foregoing factors.