  We explore the possibility of probing freeze-in dark matter (DM) produced via
the right-handed neutrino (RHN) portal using the RHN search experiments. We
focus on a simplified framework of minimally-extended type-I seesaw model
consisting of only four free parameters, namely the RHN mass, the fermionic DM
mass, the Yukawa coupling between the DM and the RHN, and a real singlet scalar
mass. We consider two cases for the DM production either via decay of the
thermal RHN or via scattering of the bath particles mediated by the RHN. In
both cases, we show that for sub-TeV scale DM masses, the allowed model
parameter space satisfying the observed DM relic density for freeze-in scenario
falls within the reach of current and future collider, beam dump and forward
physics facilities looking for feebly-coupled heavy neutrinos.
