Résumé : The microbiologically influenced corrosion (MIC) behavior of carbon steel is investigated in the presence of Vibrio and Pseudomonas. Sterilized natural seawater inoculated with Pseudomonas, Vibrio, and the mixture of Pseudomonas and Vibrio, separately, and they are utilized as the media for corrosion characterizations, which are closer to the natural environment in seawater. Weight loss measurements, electrochemical techniques (the open-circuit potential, electrochemical impedance spectroscopy (EIS), and potentiodynamic polarization curves), and surface analysis (scanning electron microscopy (SEM)) are performed to explore the synergistic effect of Pseudomonas and Vibrio on the corrosion behavior of carbon steel. As seen from the growth curves of bacteria, the growth and propagation of Pseudomonas and Vibrio are affected by their metabolic activities. Besides, the results obtained by SEM show that more severe pitting corrosion is observed on the coupons exposed to the sterilized natural seawater inoculated with the mixture of Pseudomonas and Vibrio. Further, the results from electrochemical measurements and weight loss measurements suggest that under the synergistic effect of Pseudomonas and Vibrio, the initial corrosion rate of carbon steel is inhibited, while the latter corrosion is enhanced.