Calcium carbonate is a chemical compound used in several industries due to its properties and versatility and can be obtained by extraction from sedimentary rocks. Endolithic Antarctic microbes can precipitate several minerals, including calcium carbonate. In this sense, this work evaluated the crystals produced from precipitated calcium carbonate by bacteria isolated from rocks collected in Deception Island and King George Island, maritime Antarctica. Qualitative screenings were performed to select bacteria that precipitate calcium carbonate, using acidic and basic culture media. The presence of carbonate was verified with hydrochloric acid. Scanning electron microscopy (SEM), equipped with an energy dispersive X-ray detector (EDS), was used to confirm the formation of calcium crystals. A total of 48 bacteria were isolated, most of which belonged to the genera Arthrobacter, Pseudomonas, Bacillus, and Stenotrophomonas, identified by MALDI-TOF and biochemical methodology. Of them, 45 were able to form crystals on the microbial biofilm in solid medium and also produced effervescence in the areas where the crystals formed, confirming the presence of carbonate. Thirteen isolates were able to produce calcium, confirmed by SEM. Bacillus and Stenotrophomonas were the best calcium carbonate producers. This is the first report of the evaluation of calcium carbonate bioprecipitation by endolithic bacterial strains recovered from rocks collected on Deception Island and King George Island, Antarctica. Calcium carbonate bioprecipitation can be considered an innovative strategy for microbial bioprospecting in Antarctica targeting future biotechnological applications in several sectors, including civil engineering and cosmetics.