The eggshell of green (Chelonia mydas (L., 1758)), loggerhead (Caretta caretta (L., 1758)), hawksbill (Eretmochelys imbricate (L., 1766)) and flatback (Natator depressus (Garman, 1880)) sea turtles nesting in eastern Australia were examined by scanning electron microscopy to determine if the ultrastructure was contributing to interspecific variation in fungal invasion of eggs. The eggshells of all species investigated were of similar structure (outer inorganic layer of aragonite crystals and an inner organic fibrillar layer) and similar thickness. Well-defined pores that would allow direct entry of fungal hyphae or spores were not present in any species. It was concluded that eggshell ultrastructure does not allow direct access by fungal hyphae or spores and does not contribute to interspecific variation in the vulnerability of loggerhead sea turtle eggs to fungal infection.