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Sea turtles are migratory animals that travel from foraging grounds to specific nesting beaches every few years and that, therefore, can be influenced by oceanographic conditions in several different habitats. We assessed how sea surface temperature (SST) and chlorophyll- (Chl-) within both internesting and foraging areas influence the nesting abundance, phenology and duration of internesting periods of the green turtles (Chelonia mydas) that nest at Cabuyal, Northwest Costa Rica. Specifically, we compared (1) SST and Chl- in foraging areas to the nesting abundance and median nesting date (MND) registered on the beach over seven nesting seasons and (2) SST in internesting habitats to the observed internesting period (OIP) (number of days between successful nesting events) and the MND. Nesting abundance was strongly correlated to Chl- concentrations at the main foraging area during the February preceding the nesting season. However, we found no significant effect of SST or Chl- in either foraging or internesting habitats on the MND. Mean SST values in the internesting habitats and OIP were negatively correlated and were highly variable both between and within years. Oceanographic conditions appear to strongly influence OIP and nesting abundance, but not the nesting phenology of green turtles in this area. The complex nature of the effect of oceanographic conditions on reproduction of the East Pacific green turtle suggests uncertainty in how this species will respond to climate change.