Yb3+ complexes with two nitrilotriacetic acid molecules were prepared and their compositions were determined as K3[Yb(nta)2(H2O)]*5H2O and Na3[Yb(nta)2]*6H2O by elemental analyses. Their structures were characterized by single-crystal X-ray diffraction analyses. In complex K3[Yb(nta)2(H2O)]*5H2O, the YbN2O7 part forms a nine-coordinate monocapped square antiprismatic structure. In complex Na3[Yb(nta)2]*6H2O, the YbN2O6 part forms an eight-coordinate square antiprismatic structure. It can be seen that the outer cations (K+ and Na+) greatly affect the coordination number and coordinate structure from these results.