In recent years, sodium batteries have raised interest as cheap rechargeable batteries for large format rechargeable battery applications such as the grid storage. A number of promising cathode materials has already been tested, however their electrochemical performances remain below their lithium counterpart cathodes. Complete structural and electrochemical investigations are needed to improve the characteristics of existing sodium electrode materials, design and synthesis of new ones with improved battery performance. Phosphate based materials are considered as promising cathode materials for sodium batteries due to their low cost and the variety of structural arrangements. In addition, it is predicted that phosphate cathode materials are thermally and electrochemically stable due to the presence of strong P-O bonds. The alluaudite-type structure, with the general formula AA’BB’₂(PO₄)₃ (A and A’ = Li, Na; B is a large six coordinated cation; B’ is a small six coordinated cation), has been intensively studied as electrode materials for LIBs and/or NIBs. In the present work, we report on the synthesis, characterization and electrochemical performance of a new Na_1.86Fe₃(PO₄)₃ alluaudite-type structure compound. The material delivers ~ 109 mAhg^-1 as a reversible capacity at ~ 3 V with a small capacity fade during cycling. The refinement of the structure by the Rietveld method and results of Mössbauer experiments indicate the presence of sodium deficiency and a Fe²⁺/Fe³⁺ ratio below 2/1 in the pristine material. Detailed study on the mechanism of sodium removal/insertion will be presented using X-ray, galvanometric cycling, cyclic voltammetry and Mössbauer techniques.