Background: Bats are hosts for a variety of microorganisms, however, little is known about the presence of Chlamydiales and hemotropic mycoplasma. This study investigated 475 free-living and captive bats from Switzerland, Germany and Costa Rica for the occurrence of Chlamydiales and hemotropic mycoplasma.Results: Screening for Chlamydiales was performed using a Chlamydiaceae-specific real-time PCR targeting the 23S rRNA gene and a pan-Chlamydiales PCR targeting the 16S rRNA gene resulting in a total prevalence of 31.4%. For sequencing, a PCR with the specifically designed inner primers panFseq and panRseq was performed, and criteria published by Pillonel et al. were used to classify the 19 obtained sequences, resulting in the formation of two groups. Groups one and two shared sequence identities to Chlamydiaceae and to Chlamydia-like organisms, including Rhabdochlamydiaceae and unclassified Chlamydiales from environmental samples, respectively.Analysis for the presence of hemotropic mycoplasma was performed using a universal SYBR Green hemoplasma screening real-time PCR targeting the 16S rRNA gene, real-time PCRs specific for M. haemofelis-like and 'Candidatus M. haemominutum'-like organisms and two conventional PCRs targeting an 871-bp and 1030-bp region of the 16S rRNA gene resulting in a total prevalence of 0.7%. Sequencing and phylogenetic analysis of the 871-bp and 1030-bp region of the 16S rRNA gene were used to classify positive specimens and infer their phylogenetic relationships. Three sequences with identities to other unidentified mycoplasma found in vampire bats and Chilean bats were obtained.Conclusions: Bats can harbor Chlamydiales and hemotropic mycoplasma and the newly described sequences in this study indicate that the diversity of these bacteria in bats is much larger than thought before. Both, Chlamydiales and hemotropic mycoplasmas are not restricted to certain bat species or countries and free-living as well as captive bats can be colonized. In conclusion, bats represent another potential host or vector for novel, previously unidentified, Chlamydiales and hemotropic mycoplasma.