LiCo x Mn1−x PO4/C nanocomposites (0≤ x ≤1.0) were prepared by a combination of spray pyrolysis at 300°C and wet ball-milling followed by heat treatment at 500°C for 4h in 3% H2 +N2 atmosphere. X-ray diffraction analysis indicated that all samples had the single phase olivine structures indexed by orthorhombic Pmna. The lattice parameters linearly decreased with increasing cobalt content, which confirmed the existence of solid solutions. It was clearly seen from the scanning electron microscopy observation that the LiCo x Mn1−x PO4/C samples were agglomerates with approximately 100nm primary particles. The LiCo x Mn1−x PO4/C nanocomposites were used as cathode materials for lithium batteries, and electrochemical performance was comparatively investigated with cyclic voltammetry and galvanostatic charge–discharge test using the Liǀ1M LiPF6 in EC:DMC=1:1ǀLiCo x Mn1−x PO4/C cells at room temperature. The cells at 0.05C charge–discharge rate delivered first discharge capacities of 165mAhg−1 (96% of theoretical capacity) at x =0, 136mAhg−1 at x =0.2, 132mAhg−1 at x =0.5, 125mAhg−1 at x =0.8 and 132mAhg−1 (79% of theoretical capacity) at x =1.0, respectively. While the first discharge capacity increased with the cobalt content at high charge–discharge rates more than 0.5C due to higher electronic conductivity of LiCoPO4 in comparison with LiMnPO4, the cycleability of cell became worse with increasing the amount of cobalt. The existence of Mn2+ seemed to enhance the cycleability of LiCo x Mn1−x PO4/C nanocomposite cathode.