Parachlamydia acanthamoebae has been implicated as an emerging agent of pneumonia in humans. Recently, it has been linked to miscarriage and neonatal infections. In contrast, its role in atherosclerosis remains controversial. In animals, there is strong evidence for Parachlamydia as a new abortigenic in cattle, and further data on this agent in other animal species is accumulating. New diagnostic methods, such as specific real-time PCR and immunohistochemistry with specific anti-Parachlamydia antibodies to detect the organism within lesions, are now available to facilitate the diagnosis of parachlamydial infections in humans and animals. This review discusses parachlamydial infections in clinical settings in humans and animals, as well as their zoonotic potential and possible modes of transmission. Current diagnostic tools are presented, and finally, the antibiotic susceptibility of Parachlamydia is described for potential future preventive and therapeutic options. Nevertheless, more data on Parachlamydia and Chlamydia-like organisms are needed to elucidate their host range and pathogenic potential in humans and animals.