Substitutional solid solutions Mn1-xFexNiGe (0.05≤x≤1.00) were synthesized. The crystal structure in the temperature range of 20 - 300 K has been studied by X-ray and neutron diffraction. At T = 200 K, a phase transformation from a hexagonal structure of the Ni2In type to an orthorhombic structure (S.G. Pnma) has been observed. The magnetic properties of these compounds were also investigated in the temperature range of 5 - 300 K and external magnetic fields up to 10 T. The temperature of the "magnetic order - magnetic disorder" phase transformation was found to decrease from 272 to 132 K with an increase in concentration x from 5 to 30 mol%.