Topological quantum phenomena due to the presence of both Dirac fermions and flat bands in Kagome semimetal CoSn promise novel transport properties. In Kagome materials, the transport properties can be enhanced by moving the position of the flat band and Dirac fermions with doping. Here, we have investigated the magnetotransport and electronic properties by Fe doping in CoSn. A large positive magnetoresistance (MR) of ≈105% at 3 K and 8 T magnetic field has been observed in CoSn. Fe doping in Co1-x FexSn gives rise to negative MR with a large negative value for x = 0.2 (-8.4%) but decreases for x = 0.3 (-3.7%) and x = 0.4 (-2.7%). Tuning of MR from positive to negative values with Fe doping in CoSn is associated with the changes in energy position of the localized flat band and emergence of quasi-localized states near the Fermi level. The systematic variation of MR with increasing x depends both on the structural changes due to increase in the lattice parameters and on the near neighbor interac- tions of the Sn atoms with the Co atoms in the Kagome plane. The origin of quasi-localized states is associated with the electron hopping and the variation in the strength of localization with doping that leads to tunable MR properties in Co1-x FexSn.