The title compound, penta-caesium nona-stannide hydroxide tetra-ammonia, crystallized from a solution of CsSnBi in liquid ammonia. The Sn9 (4-) unit forms a monocapped quadratic anti-prism. The hydroxide ion is surrounded by five caesium cations, which form a distorted quadratic pyramidal polyhedron. A three-dimensional network is formed by Cs-Sn [3.8881 (7) Å to 4.5284 (7) Å] and Cs-NH3 [3.276 (7)-3.636 (7) Å] contacts.