A psychrotrophic bacterium Shewanella sp. strain SIB1 was grown at 4 and 20 °C, and total soluble proteins extracted from the cells were analyzed by two-dimensional polyacrylamide gel electrophoresis. Comparison of these patterns showed that the cellular content of a protein with a molecular mass of 28 kDa and an isoelectric point of four greatly increased at 4 °C compared to that at 20 °C. Determination of the N-terminal amino acid sequence, followed by the cloning and sequencing of the gene encoding this protein, revealed that this protein is a member of the FKBP family of proteins with an amino acid sequence identity of 56% to Escherichia coli FKBP22. This protein was overproduced in E. coli in a His-tagged form, purified, and analyzed for peptidyl-prolyl cis-trans isomerase activity. When this activity was determined by the protease coupling assay using N-succinyl-Ala-Leu-Pro-Phe-p-nitroanilide as a substrate at various temperatures, the protein exhibited the highest activity at 10 °C with a kcat/Km value of 0.87 µm−1·s−1. When the peptidyl-prolyl cis-trans isomerase activity was determined by the RNase T1 refolding assay at 10 and 20 °C, the protein exhibited higher activity at 10 °C with a kcat/Km value of 0.50 µm−1·s−1. These kcat/Km values are lower but comparable to those of E. coli FKBP22. We propose that a FKBP family protein is involved in cold-adaptation of psychrotrophic bacteria.