This article provides a comprehensive review of the literature on the nature and evolution of rural livelihood diversification in sub-Saharan Africa, and the situation regarding smallholders. It reveals mixed findings about the causes and consequences of livelihood diversification on rural smallholders adopting this strategy. A lot of evidence from the literature suggests that it is relatively better-off smallholders with sufficient assets who achieve successful livelihood diversification, mainly by exploiting opportunities and synergies between farm and nonfarm activities. Because of asset constraints, increase in incomes and wealth based on livelihood diversification has not yet benefitted the large majority of smallholders.