This thesis examines the effectiveness of transboundary water regimes. Water is the only scarce resource for which there is no known substitute. However, ecological sustainability of shared water resources is being lost in many countries as current international frameworks suffer from differences that exist between institutional functions, practices, objectives, and bio-physical properties. To address this gap, this thesis starts from the premise that analyses of the effectiveness of transboundary water regimes are capable of shedding light to prescribe transboundary water governance. This thesis explores effectiveness of a transboundary water regime in Africa, principally the Lake Victoria Basin, home to largest freshwater lake in Africa, and second largest lake in the world. It is an important source of local and international freshwater fisheries, benefiting about 35 million people locally. As such, the basin provides a globally significant but surprisingly under-researched venue for testing theoretical interpretations of transboundary water regime effectiveness using state of the art methodological approaches. By employing a Regime Analytic Levels Process model, never used before, data were collected through elite interviews and documentary analysis, analyzed, and then synthesized. The results are as follows. The regime creation process (inputs) was dominated by process factors mainly in implementing the operational directives of donors and development partners, rather than understanding the underlying problem factors. The regime architecture analysis (outputs) suggests that procedural (rather than substantive) characteristics formed the basis of the regime’s architecture. The regime impacts analysis shows the regime underperformed in relation to those components that addressed substantive concerns. The global effectiveness of the regime was 41.6 per cent, basically procedural in character. This suggests it failed to establish a ‘duty of care’ with insufficient ‘programme of measures’ that governed the conduct of actors in the long term. These findings suggest the regime is not sustainable. The following recommendations are suggested: to focus donor effort on substantive characteristics to socialize actors via a ‘duty of care’; to establish secure sources of funding to support long-term efforts; to merge the regime with wider national-level activities in the basin; and to establish a sufficient programme of measures, inform and prevent.