ABSTRACT Although there is consensus among academics and policy makers that how we grow and distribute food needs to be more sustainable, the most appropriate ways of doing so remain unclear and are at times deeply contested. Over the last decade, two vastly different approaches to food security and sustainability have become increasingly prominent in Sub-Saharan Africa. One is the African Green Revolution, implemented by a consortium of partners comprised of African governments, the private sector, philanthropic donors, and multilateral institutions. The other is the African food sovereignty movement, headed by Africa's peasant unions and civil society organizations. The ontological backgrounds of these two agrarian models inevitably influence their respective approaches to food security and sustainability in the different regions of Sub-Saharan Africa. The African Green Revolution is bent in favor of modern rationalist notions about structural transformation and development. The food sovereignty model is inspired by historical structural theories that tackle issues of power and (in)justice embedded within global political and economic structures. These diametrically opposed ideological foundations help to explain the polarization and tensions that exist between the two models. Such tensions, however, also hinder fruitful discussion about how to effectively address key concerns in Africa's food systems. To advance the academic debates, this dissertation explores the following question: in what ways can sustainability assessment frameworks give insights into the potential contributions of the African Green Revolution and food sovereignty approaches to food security and sustainability in rural Mozambique? This study had three research objectives: (1) to refine conceptually and apply a sustainability assessment framework that merges key food security and sustainability goals in southern Africa's food and agricultural systems; (2) to better understand the perspectives of stakeholders implementing the African Green Revolution and the food sovereignty models as well as the farmers that they serve to determine what each model offers in terms of food security and sustainability; and (3) to tease out the implications of the two models' activities on the ground, including their potential impact on food and agricultural policies. In 2014 and 2015, fieldwork was conducted in Mozambique, where both agrarian models are being implemented by two organizations. The African Green Revolution is supported by the Alliance for a Green Revolution in Africa (AGRA), and the food sovereignty model is represented by the National Union of Mozambican Peasants (UNAC).The field-research was designed to comparatively assess how the activities of these two organizations contribute to food security and sustainability from farmer perspectives. Various techniques were used to gather data, including a comprehensive literature review, semi-structured interviews with key informants (n=71) and participant observations. The research identified five interrelated sustainable food system indicators that were informed by farmer perspectives and sustainability assessment literature: access to quality seeds, activities to improve soil health, income opportunities, land rights and policy engagement. Taken together, these indicators can help to address both the technical aspects of meeting food security (issues of production) and the policy and political economy issues that facilitate (or hinder) the means to achieving food security. The research finds that the African Green Revolution and food sovereignty models respond to the needs of Mozambican smallholder farmers in more complex and nuanced ways than mainstay discussions in academic and public forums reveal. While some scholars and actors contend that the African Green Revolution and food sovereignty models are incongruent, Mozambican smallholder farmers utilize some of the resources that the models offer in complementary rather than competing ways. Neither model addresses critical components of food security and sustainability in their entirety. Where possible, farmers engage both models-taking from each what helps them to meet these two goals. The conflicting interplay between the African Green Revolution and the food sovereignty movement at the broader political-economy level, versus farmers' complementary engagement with the two models, illustrates that meeting food security and sustainability objectives is, in some contexts, messy. This realization suggests a need for further research, particularly on options that may serve broad-based sustainability goals in Africa's food systems.