The upgrading of biomass-derived feedstocks to liquid transportation fuels is complex because of the chemical differences between biomass-derived chemicals and conventional fuels. Aldol condensation may play an important role in converting biomass-derive components to fuels because it allows smaller species to be converted to larger species that are more similar to conventional fuels. This review covers recent progress in aldol condensation of biomass-derived 5-hydroxymethylfurfural, acetone, methyl ketones, acetoin, levulinic acid, furfural, cyclopentanone and levulinic acid. The corresponding catalytic mechanisms and future research directions in these areas are also discussed.