In Cameroon, cocoa systems are created at the margins of the forest with trees associated to cocoa. Cocoa systems integrate forest trees retained during land clearing for field preparation and other trees planted by farmers for their role and uses (regulation of light, moisture, soil fertility, etc.). Fruits, non-timber forest products, and timber are part of farmers’ livelihood strategies for cash revenues and other services. One of the major factors of deforestation is the expansion of cocoa systems in a context of population growth (2.5%). National cocoa production is currently around 250.000 t, and average farm production is 350 kg/ha. Production is low due to many challenges, including poor soil fertility and poor management. Currently, the expansion of cocoa systems is done beyond the forest margins and the practices of maintaining or planting trees in the cocoa system is gradually decreasing. Keeping trees in a cocoa system was formerly based on farmers’ knowledge. The biological and ecological characteristics of suitable tree species to be associated with cocoa for soil fertility, cocoa productivity, livelihoods, and carbon stocks are poorly known. Therefore, this PhD project aims to determine the ecological and biological characteristics of tree species to plant or maintain in a cocoa system for high cocoa productivity, soil fertility, carbon stocks, and livelihoods. This information can help update the cocoa national policy currently in force in Cameroon and promote sustainable cocoa systems which integrate more efficient land use, soil protection and fertility, higher yields and income, and biodiversity conservation. This project will also help identify and describe a group of trees suitable to cocoa for high sustainable productivity, tree diversity, soil fertility management, and more efficient land use and forest conservation. Finally, the project will evaluate forms of intensification and sustainable integrated cocoa systems in the forest margins of Cameroon and around the Congo basin forest to propose different models of suitable tree or group of trees to associate with cocoa for forest conservation in a sustainable, intensified and integrated cocoa production system.