  We present a simple extension of the standard model (SM) to explain the
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 $Z_2$ symmetry. These vector-like
leptons 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 component of the Universe. We
show the relevant parameter space for correct relic density and direct
detection of dark matter.
