Southern Ocean ecosystems are extremely vulnerable to sea-ice changes occurring at different spatial and temporal scales. Variability in the sea-ice conditions strongly influence the survival and reproduction of animals that are synchronized with the seasonality of sea ice. Although the linkages between Adelie penguins (Pygoscelis adeliae) and sea-ice conditions are well established, the spatial and temporal scales at which sea ice affects individuals and populations are poorly known. Using 23years of penguin breeding success and remote-sensing data of sea ice, we investigate the spatial and temporal scales at which sea-ice changes best explain variations in the reproductive success of Adelie penguins at Pointe Geologie, East Antarctica. The best spatial scale encompassed all foraging areas exploited and all the sea-ice conditions encountered by penguins over a breeding season. There was a consistent influence of sea-ice concentration during the guard stage on the overall breeding success. We demonstrate the importance of considering sea ice at a fine temporal scale rather than using an average value over the breeding season to best explain reproductive success in Adelie penguins.