The present study aimed to determine and compare the bioaccumulation of heavy metals in two freshwater species of mussels Unio elongatulus eucirrus (Bourguignat, 1860) and Dreissena polymorpha (Pallas, 1771) in Keban Dam Lake, Turkey. The amount of Arsenic (As), Cadmium (Cd), Copper (Cu), Lead (Pb) and Uranium (U) were detected. Heavy metals concentrations (ppm) of these heavy metals in U. e. eucirrus and D. polymorpha were 1.071 and 1.376 for As, 0.174 and 0.335 for Cd, 0.004 and 3.817 for Cu, 0 and 0.267 for Pb, 0.004 and 0.267 for U, respectively. Arsenic concentrations in the tissues of both species have exceeded the maximum permission limits in all sampling sites. The concentrations of Cu and U were considerably greater in D. polymorpha specimens than in U. e. eucirrus (p<0.05). The results obtained from the present study showed that both species accumulated heavy metals generally in the following sequences: Cu > As > Cd > Pb >U. The present results indicated that D. polymorpha may be a better bioindicator of environmental pollution than U. e. eucirrus, since it showed a higher accumulation capacity.