We investigated the effect of Cu exposure on the activities of protective antioxidant enzymes in the gills and digestive glands of the manila clam Ruditapes phillippinarum exposed to subchronic concentrations (0, 20, 40, and $80{mu}gL^{-1}$) of waterborne Cu. No mortality occurred during the experimental period, and no significant condition index differences were observed in any exposure group compared with the control. No significant differences were observed in the digestive glands and gills of the clams observed during 15 days of exposure, but after 30 days, the SOD activity in the gill showed a significant difference between the $80{mu}gL^{-1}$ Cu-exposed group and the control. GPx activities in the digestive glands and gills were significantly lower after 30 days of Cu exposure. Gill GR activity in the high-exposure group ($80{mu}gL^{-1}$) was significantly elevated compared with that in the control group. GST activities in the digestive glands of all groups did not change over 30 days. However, GST activity in the gill at $80{mu}gL^{-1}$ Cu was significantly higher after 15 and 30 days of exposure. GSH activities in the gill showed patterns similar to those of GST activities during exposure periods. In the digestive glands, GSH activity was higher only at $80{mu}gL^{-1}$ after 30 days exposure. In digestive glands and gills, the MDA levels of clams exposed to $80{mu}gL^{-1}$ Cu were significantly higher after 30 days of exposure.