Two new polymorphs, beta- and gamma-In2Ge6O15(NH2CH2CH2NH2)(2), have been synthesized under solvothermal conditions using 2-methylpentamethylenediamine as a solvent and structurally characterized by single-crystal X-ray diffraction. Both structures contain single layers with the composition [Ge6O15] that are connected by In2O6N4 octahedral dimers to form 3D frameworks. The germanate layers contain four-, six-, and eight-membered rings and six-membered rings in the beta and gamma polymorphs, respectively. Compounds with related structures are discussed for comparison.