We compared changes, induced by the addition of 100 nM and 5 mM glucose in the proteome and metabolome complements in several strains of Synechococcus and Prochlorococcus, growing either under standard light conditions or darkness. Our results demonstrate that glucose is being metabolized by these cyanobacteria, using mainly the oxidative pentoses pathway, while no evidence was found for the involvement of the Entner-Doudoroff pathway in this process. We observed differences in the metabolic strategies for glucose utilization, both between genera, and between Prochlorococcus MED4 and SS120 strains, which might be related to their specific adaptations to the environment. Our results also suggest that marine cyanobacteria can detect nanomolar glucose concentrations in the environment and that glucose might be used to sustain metabolism under darkness.