Strain A-3, an amylase-producing bacteria, was isolated from coastal seawater near Daecheon in the Republic of Korea. It was seen to possess a single polar flagella and grow well, on ASW-YP agar plates, at temperatures of between 20-37°C. However, it grew more slowly at the temperatures of 15°C and 40°C. Similarly, it was observed to grow abundantly, in an Artificial Sea Water-Yeast extract-Peptone (ASW-YP) liquid medium, in a pH range of 6-9, but not grow at pHs of 4-5 and a pH of 10. Strain A-3 was noted as being close to Pseudoalteromonas phenolica O-BC30 , Pseudoalteromonas luteoviolacea NCIMB1893 , Pseudoalteromonas rubra ATCC29570 , and Pseudoalteromonas byunsanensis FR1199 , with 98.30%, 97.86%, 97.78%, and 97.25%) similarities respectively, in its 16S rRNA sequence. A phylogenetic tree revealed that strain A-3 and P. phenolica O-BC30 belong to a clade. However, strain A-3 differed from P. phenolica O-BC30 in relation to a number of physiological characteristics. Strain A-3 exhibited no growth above 5% NaCl concentrations, no utilization of D-glucose, D-mannose, D-maltose, or D-melibose, and no lipase (C-14) activity. All of these properties strongly indicate that strain A-3 is distant from P. phenolica O-BC30 and thus led us to name it Pseudoalteromonas sp. A-3. Pseudoalteromonas sp. A-3 produces α-amylase throughout growth. Maximal amylase activities of 144.48 U/mL and 149.20 U/mL were seen at pH 7.0 and 37°C, respectively. Pseudoalteromonas sp. A-3's high, stable production of α-amylase in addition to its biochemical features, such as alkali-tolerance, suggest that it is a good candidate for industrial applications. © The Korean Society for Microbiology and Biotechnology.