© 2021, The Author(s).In this paper, we present the one-loop radiative corrections to the electroweak precision observable ? ? coming from the IW= 1 multiplet excited leptons. We have calculated the couplings of the exotic lepton triplet to the vector bosons and ordinary leptons using the effective Lagrangian approach. These couplings are then used to estimate the excited lepton triplet contribution to the ? ? parameter. The mass degenerate excited lepton contribution to ? ? is small and can be neglected. However, if the excited leptons are non-degenerate, their contribution can be large which can result in more stringent constraints on the excited fermion parameter space compared to the constraints from present experimental searches and perturbative unitarity condition.