The spinel series Ge _x Cu_1–x Fe₂O₄ (x=0.0 to 0.9) has been studied in detail by means of Mössbauer spectroscopy, X-ray diffraction and magnetization measurements at room temperature (298 K). Analysis of X-ray diffraction intensity data and Mössbauer intensity data suggest that this system remains in single phase up tox=0.4 then it phase separates into two different phases forx=0.5 to 0.9. Lattice constants of this system deviate from Vegard's law. Mössbauer spectra for x=0.0 to 0.4 suggest the existence of two hyperfine fields, one due to the Fe³⁺ tetrahedral ions (A-sites) and the other due to the Fe³⁺ octrahedral ions (B-sites), while forx=0.5 to 0.9 it gives Mössbauer patterns corresponding to two separate phases. The systematic composition dependence of quadrupole interactions and nuclear hyperfine fields of⁵⁷Fe³⁺ ions also support the concept of phase separation forx=0.5 to 0.9. The observed variation of⁵⁷Fe³⁺ hyperfine field on A- and B-sites withx forx=0.0 to 0.4 can be explained qualitatively on the basis of supertransferred hyperfine interactions.