The magnetoelectric coupling mechanism in Ni/BiFe0.95Mn0.05O3 heterostructures is investigated through a detailed microstructural study of the BiFe0.95Mn0.05O3 film and a chemical analysis of the Ni/BiFe0.95Mn0.05O3 interface. The four structural variants expected in BiFe0.95Mn0.05O3 are detected by high resolution X-ray diffraction reciprocal space mapping method. The ferroelectric domain structure is imaged with transmission electron microscopy. Oxidized Ni is evidenced at the Ni/BiFe0.95Mn0.05O3 interface by electron energy loss spectroscopy and X-ray photoemission spectroscopy, although the degree of Ni oxidation is independent of the magnetoelectric state of the heterostructure.