Pamidronate (3-ammonium-1-hydroxypropylidene-1,1-bisphosphonate) is used clinically in the treatment of diseases affecting bone tissue. In the salt zinc pamidronate dihydrate, Zn²⁺·2C₃H₁₀NO₇P₂^-·2H₂O, pamidronate is a zwitterion with an overall charge of -1. The carbon chain adopts a trans conformation, separating maximally the positively charged N atom from the negative phosphonate groups. The Zn²⁺ ion lies on an inversion center and is surrounded by a sixfold coordination sphere provided by two bidentate chelating zwitterions and two water molecules. The bidentate O⋯Zn⋯O bond angle is 92.70 (7)°, while the O⋯O bite distance is 3.018 (3) Å.