[Objectives]  To investigate the phenotypic characteristics of Carnobacterium maltaromaticum, one of the dominant cultivable bacterial species in the larval gut of the diamondback moth, Plutella xylostella. [Methods]  The phenotype of C. maltaromaticum was analyzed with BIOLOG phenotype MicroArray (PM). A total of 950 different metabolic phenotypes were tested using PM plates 1-10. [Results]  C. maltaromaticum was able to metabolize 34.74% of the tested carbon sources, 99.47% of nitrogen sources, 100% of sulfur sources, and 79.66% of phosphorus sources. Most informative utilization patterns for carbon sources of C. maltaromaticum were organic acids and carbohydrates, and for nitrogen were various amino acids and peptides. The bacterium did not have different biosynthetic pathways but was highly adaptable and continued to metabolize in osmolytes with up to 10% sodium chloride, 6% potassium chloride, 5% sodium sulfate, 20% ethylene glycol, 6% sodium formate, 7% urea, 8% sodium lactate, 200 mmol/L sodium phosphate (pH 7.0), 200 mmol/L sodium benzoate (pH 5.2), 100 mmol/L ammonium sulfate (pH 8.0), 100 mmol/L sodium nitrate, and 100 mmol/L sodium nitrite. It could not, however, grow in media with 9% to 12% sodium lactate. It had an active metabolism at pH values between 5 and 10, with an optimal pH of around 10.0. In the presence of various amino acids, C. maltaromaticum showed deaminase activity but no decarboxylase activity. [Conclusion]  Phenotypic characterization of C. maltaromaticum has increased our knowledge of this bacterium and also revealed useful information on its function and the interaction between it and its host.