There is an increasing emergence of antibiotic-resistant Vibrio alginolyticus, a zoonotic pathogen that causes mass mortality in aquatic animals as well as human infection; therefore, there is a demand for alternatives to antibiotics for treatment and prevention of infections caused by this pathogen. One possibility is through the exploitation of bacteriophages. In the present study, the bacteriophage pVa-21 belonging to Myoviridae, was isolated and characterized as a candidate biocontrol agent against V. alginolyticus. Its morphology, host range and infectivity, growth characteristics, planktonic or biofilm lytic property, stability under various conditions, and genome were investigated. Its latent period and burst size were estimated to be approximately 70 min and 58 plaque-forming units/cell, respectively. In addition, phage pVa-21 could inhibit bacterial growth both in the planktonic and biofilm state. Furthermore, phylogenetic and genome analyses revealed that the phage is closely related to ‘phiKZ-like phages’ and can be classified as a new member of the phiKZ-like phages that infect bacteria belonging to the family Vibrionaceae.