The emperor penguin, an iconic species threatened by projected sea ice loss in Antarctica, has long been considered to forage at the fast ice edge, presumably relying on large/yearly persistent polynyas as their main foraging habitat during the breeding season. Using newly developed fine‐scale sea icescape data and historical penguin tracking data, this study for the first time suggests the importance of less recognized small openings, including cracks, flaw leads and ephemeral short‐term polynyas, as foraging habitats for emperor penguins. The tracking data retrieved from 47 emperor penguins in two different colonies in East Antarctica suggest that those penguins spent 23% of their time in ephemeral polynyas and did not use the large/yearly persistent, well‐studied polynyas, even if they occur much more regularly with predictable locations. These findings challenge our previous understanding of emperor penguin breeding habitats, highlighting the need for incorporating fine‐scale seascape features when assessing the population persistence in a rapidly changing polar environment. Plain Language Summary Polar ecosystems are threatened by future loss of sea ice. The availability of satellite sea ice products has facilitated a better assessment of the impact of sea ice on polar species. Yet most studies have focused on coarse spatial scale sea ice products hampering an understanding of the mechanisms by which sea ice affects species. The development of fine‐scale sea ice products now provides an unprecedented opportunity to better understand the responses of sea ice obligate species to climate change. The emperor penguin is an iconic species threatened by projected sea ice loss in Antarctica. Here we used fine‐scale satellite sea ice observations to understand the emperor penguin's sea ice habitat during the entire breeding and Antarctic winter season. Sea ice characteristics affect both the foraging routes and effort of polar species, with consequences for their reproduction and survival, ultimately affecting population dynamics and species persistence. Emperor penguins dived at the edge of the landfast sea ice in cracks, flaw leads and open water areas called polynyas, formed by winds on both long and short time scales. By using daily passive microwave observations, we identified that emperor penguins did not venture into the large/persistent polynyas but dived instead in the ephemeral polynyas associated with daily changes in wind direction. Key Points Dynamic fine‐scale sea icescape in East Antarctica affects the foraging routes and effort of emperor penguins during the breeding season Emperor penguins used short‐term ephemeral polynya openings to forage during the breeding season instead of using the persistent ones The breeding foraging habitat was consistent among months, years, sexes, and sites despite the highly dynamic sea ice environment