Background In recent years, Antarctica has become a key source of biotechnological resources. Native microorganisms have developed a wide range of survival strategies to adapt to the harsh Antarctic environment, including the formation of biofilms. Alginate is the principal component of the exopolysaccharide matrix in biofilms produced by Pseudomonas, and this component is highly demanded for the production of a wide variety of commercial products. There is a constant search for efficient alginate-producing organisms. Results In this study, a novel strain of Pseudomonas mandelii isolated from Antarctica was characterized and found to overproduce alginate compared with other good alginate producers such as Pseudomonas aeruginosa and Pseudomonas fluorescens. Alginate production and expression levels of the alginate operon were highest at 4°C. It is probable that this alginate-overproducing phenotype was the result of downregulated MucA, an anti-sigma factor of AlgU. Conclusion Because biofilm formation is an efficient bacterial strategy to overcome stressful conditions, alginate overproduction might represent the best solution for the successful adaptation of P. mandelii to the extreme temperatures of the Antarctic. Through additional research, it is possible that this novel P. mandelii strain could become an additional source for biotechnological alginate production.