An increase in the level of atmospheric carbon dioxide (CO2) and the resultant rise in CO2 in seawater alter the inorganic carbon concentrations of seawater. This change, known as ocean acidification, causes lower pH in seawater and may affect the physiology of seaweed species. Accordingly, the main goal of the current study was to determine the physiological responses of Bryopsis plumosa to elevated-CO2. The results indicated that photosynthesis of B. plumosa was insignificantly affected to elevated-CO2, but photosynthetic pigment contents and phenolics were significantly decreased. The results obtained from the research reveal that B. plumosa may become physiologically advanced when exposed to CO2-induced ocean acidification. In particular, B. plumosa may be more able to compete with calcifying algae when it will become future predicted CO2 scenario.