Full-sun cocoa farming is currently the most widespread cocoa cultivation system in humid and sub-humid Côte d’Ivoire. Higher short-term yields from increasing surfaces under cultivation in this farming system have contributed to the country being ranked as top cocoa producer in the world. However the negative consequences including biodiversity loss, soil fertility depletion and soil quality degradation associated with this system, have incredibly received so less attention that the type and magnitude of such agro-ecological consequences within the current context of climate change are worth investigating. The present study was undertaken in the former cocoa belt of Central-Western Côte d’Ivoire, precisely in the Oumé Department. The main objective was to assess the impact of forest conversion to full-sun cocoa plantations on above and below-ground biodiversity along with soil quality by measuring chemical, physical and biological parameters along a chronosequence of different ages (5, 10 and 20 years). The results are summarized as follows: (i) the conversion of semi-deciduous forests to cocoa plantations resulted in plant diversity and species richness loss due to the disappearance of a huge number of native species while earthworm abundance and species richness increased due to the appearance of species adapted to degraded lands, (ii) soil quality was severely impaired by cocoa farming with the worse scenario being found under the 10-year-old cocoa plantations, where SOC, total N, CEC contributed mostly to soil quality degradation. The contribution of these findings to devise options for sustainable tree-based cocoa farming is discussed.