DNA damage caused by endogenous and exogenous factors, if left unrepaired, can have a negative effect on organismal fitness and at last the survival of species. Multiple mechanisms of DNA repair are vital for efficient repair of damaged DNA. Archeae, which belong to the third domain od life are known for inhabiting a very broad range of extreme environments. They are believed to be eukaryotes’ ancestors. However, because of the complexity of cultivating archaeal species in the laboratory, little was known about their DNA repair mechanisms. With the rapid development of DNA sequencing and metagenomics, the research of archaea has been made significantly easier resulting in the discovery of many similarities between archaeal and prokaryotic and eukaryotic genes. With research being made easier, mysteries held by the third domain of life have started to be unraveled. Throughout this thesis, I will review three DNA repair mechanisms: mismatch repair, nucleotide excision repair, and double-strand break repair dependent on homologous recombination. I will also highlight the complexity of these DNA repair mechanisms, the cooperation between proteins involved in DNA repair, and the significance of researching DNA repair pathways in archaea.