  In this paper, we studied the phenomenological consequences of recently
proposed swampland conjecture on the inflationary models though constraints on
reheating. If dark matter is assumed to be produced during reheating, the
conjecture will provide further constraints on the dark matter parameter space
through its current relic abundance. As has been pointed out already and also
analyzed in our present paper any successful inflationary scenario is in clear
tension with the aforementioned conjecture in its current form. However
considering the swampland parameters to be free and constrained by the
inflationary observables, we studied in detail its consequence on the reheating
and dark matter phenomenology. We point out the connection between swampland
conjecture and the scalar spectral index $n_s$ by PLANCK within current $2
\sigma$ range, and associated constraints imposed on the reheating temperature
and the dark matter annihilation cross-section.
