X-ray powder diffraction data, unit-cell parameters, and space group for calcium(II)–naproxen complex, C28H26CaO6·2H2O, are reported [a = 36.918(2) Å, b = 5.655(6) Å, c = 12.505(6) Å, β = 91.263(2)°, cell volume V = 2610.47 Å3, Z = 4, and space group C2]. All measured lines were indexed and are consistent with the C2 space group. No detectable impurities were observed.