We report the electrochemical properties of carbon-coated particles of MnxFe1-xPO4 (0 <= x <= 1), a group of promising cathode's materials for sodium-based batteries. The MnxFe1-xPO4 materials have been obtained by electrochemical delithiation of LiMnxFe1-xPO4 and their electrochemical properties have been evaluated in Na cells. The mechanism of Na insertion/extraction strongly depends on the amount of manganese in the structure: at low amount of Mn (x <= 0.2) there is no specific domain associated to the electrochemical activity of Mn; at high amount of Mn (x >= 0.5) one can distinguish two voltage regions, one linked to the Mn2+/Mn3+, and the other one to the Fe2+/Fe3+ redox couples. (C) 2016 The Electrochemical Society. All rights reserved.