Alginate is a hydrocolloid naturally sourced from brown seaweeds. Its oligomerized forms have growing industrial importance with applications in food, pharmaceutical, and material products. The breakdown of alginate is shaped by the facile decomposition of alginolytic bacteria. Although enzymes for alginate degradation are highly sought after (primarily the alginases), species identification of these bacteria is seldomly determined. The aim, therefore, of this study was to molecularly identify the potential alginolytic bacteria from partially decaying Sargassum polycystum collected from Calatagan, Batangas, Philippines. Phylogenetic analysis of 16S rRNA sequences showed that bacterial isolates belong to Klebsiella pneumoniae and Vibrio alginolyticus. The resulting molecular data was supported by various culture tests with indications of alginate degradation activities. Supporting data and/or tests (biochemical and gene expression studies) should be done to definitively confirm the alginate-degrading property of these bacteria. The utility of sequence data for species identification on bacterial isolates improved the ability to assign species names over traditional methods. The findings in this study point toward providing important microbiological resources useful for various industrial applications of alginase.