One of the potential sources of Vibriosis of oyster larvae in hatcheries is contaminated microalgae feed. Antibiotics have been used to prevent the proliferation of Vibrio spp. in hatcheries but this is discouraged due to detrimental effects on the environment and the potential for antibiotic resistant bacteria to develop. Accordingly, the use of bacteriophages as an environmentally friendly biological treatment to control bacterial contamination has value for the shellfish industry. In this study, we demonstrate that bacteriophages can be effectively used in controlling the Vibrio spp. contamination on microalgae broth. A Vibrio alginolyticus strain, which is pathogenic to oyster larvae, was isolated from an oyster hatchery in Port Stephens Fisheries Institute, NSW, Australia. Four different polyvalent Vibrio phages (belonging to Myoviridae viral family) were successfully isolated from marine water at the Sunshine Coast region, Australia. The bacteriophages were then applied as a cocktail for the treatment of pathogenic Vibrio spp. contaminating a microalgae suspension. Significant decreases in the Vibrio spp. concentration were observed within 2 h, suggesting that the direct application of the phages to the aquaculture water could be an effective method in reducing the potential for Vibriosis in oyster hatcheries.