Background: Influence of oxygen non-stoichiometry on magnetic and electric properties of the compounds has not almost been studied yet. Aim: Synthesis of a number of the NdSr2Mn2O7+delta samples subjected to various thermal processing in air atmosphere and investigation of their structure, oxygen non-stoichiometry, electrical and magnetic properties. Method: The compounds obtained have been characterized by using X-ray diffraction (XRD) analysis, a modified gravimetric method, vibrating sample magnetometry (VSM) and standard DC four-probe method. Results: It was established that additional firing of the samples at different temperatures leads to essential changes in the oxygen non-stoichiometry. The noticeable magnetoresistance (MR) effect is observed for all the compounds below 200 K and increases monotonically as the temperature decreases. The MR values for the compounds as a function of oxygen content vary nonlinearly. The largest MR value of 380% at the 5K and magnetic field of 7T was achieved for the sample with the oxygen non-stoichiometry of delta = 0.03. Conclusions: The results observed are discussed in the assumption of ferromagnetic cluster formation in the compounds. (C) 2015 Elsevier Ltd. All rights reserved.