We present an in-depth study on the structure and magnetic properties of a novel layered oxide, Ca2Fe0.875Cr0.125GaO5. Structural studies from laboratory X-ray diffraction, synchrotron powder X-ray diffraction and neutron powder diffraction reveal that the compound crystallizes in an orthorhombic Brownmillerite phase with Pnma space group having Fe/Cr – octahedral layers and Ga – tetrahedral layers with around 9.0% of Fe occupying tetrahedral sites. The temperature evolution of Neutron powder diffraction confirms the absence of any structural changes in the range 300–6 K. Magnetic characterizations show antiferromagnetic ordering at room temperature and the co-existence of antiferromagnetic and ferromagnetic phases at low temperature. The magnetic structure derived from neutron powder diffraction is a G-type antiferromagnetic. The ordered magnetic moments at 6 K on the octahedral and tetrahedral sites are 3.15 (2) µB/cation and 0.93 (4) µB/cation, respectively oriented in the ac-plane. © 2018 Elsevier Inc.