Human activities since the beginning of the industrial age have greatly increased the amount of carbon dioxide in the atmosphere. Increased levels of atmospheric carbon dioxide have already caused a 0.1-U decline in global ocean pH, and a continuing decline of 0.3–0.5 U is predicted by the end of 2100. Acidification of the oceans has widespread effects on marine organisms, including reduced rates of calcification and interruptions to normal physiological functions. This study used gaseous carbon dioxide to maintain seawater at 2 treatment levels of pH: 7.8 and 7.6. When compared with controls held at pH 8.1–8.2, pearl oysters (Pinctada fucata, Gould) held at pH 7.8 and pH 7.6 showed no significant difference in the number of byssal threads produced or total distance traveled. Byssal threads produced by oysters in the pH 7.6 treatment were significantly thinner than those produced by oysters in the control. However, it is postulated that this was a result of the acute stress of transfer to treatment conditions and not a result of physiological stress caused by near-future levels of ocean acidification. The potential for P. fucata to adapt to near-future levels of ocean acidification is discussed.