Within the growing order of Chlamydiales, there are a number of pathogens. One is Chlamydia psittaci, a zoonotic pathogen, with birds as natural hosts that may be transmitted to humans and cause severe respiratory disease, psittacosis. The prevalence of this pathogen in Antarctic birds is almost unknown as well as the ramifications of its potential spread in na < ve bird populations. To investigate the prevalence of chlamydia organisms, cloacal and fecal samples were collected from 264 penguins and 263 seabirds on the Antarctic Peninsula and in Southern Chile. No C. psittaci could be detected by 23S rRNA real-time PCR. However, DNA sequencing of the 16S rRNA 298-bp signature sequence revealed a Chlamydiaceae-like bacterium previously found in seabirds from the subarctic zone, demonstrating that this not yet fully characterized bacterium is widespread. In conclusion, the prevalence of C. psittaci among wild birds on the Antarctic Peninsula seems to be low, but other types of chlamydial organisms are common. Further studies are required to taxonomically define and finally understand the role of these non-classified Chlamydiae.