Nanocrystalline Mn-substituted lithium ferrites were synthesized by sol–gel method. The structural data show that, the cubic phase was converted into tetragonal phase observed by XRD analysis. X-ray photoelectron spectroscopy has been used to characterize valence state of materials and the composition of the products. The electrical property study was carried out by using two probe methods and it is revealed that the all Mn substituted ferrites are semiconducting in nature. Thermoelectric power measurement also confirms 1.5⩽ x ⩾0.0 N-type and 2.5⩽ x ⩾2.0 shows the P-type semiconducting nature of Mn-substituted lithium ferrites. The effect of manganese substitution in lithium ferrites has a crucial role on the structural and electrical properties of the system.