We present a simple extension of the Standard Model (SM) to explain the recent diphoton excess, reported by CMS and ATLAS at CERN LHC . The SM is extended by a dark sector including a vector-like lepton doublet and a singlet of zero electromagnetic charge, which are odd under a Z2 symmetry. The charged particle of the vector-like lepton doublet assist the additional scalar, different from SM Higgs, to decay to di-photons of invariant mass around 750 GeV and thus explaining the excess observed at LHC . The admixture of neutral component of the vector-like lepton doublet and singlet constitute the dark matter of the Universe. We show the relevant parameter space for correct relic density and direct detection of dark matter.