  We study the impact on leptogenesis of Higgs portal couplings to a new scalar
singlet. These couplings open up additional $CP$-violating decay channels for
the higher mass singlet neutrinos $N_2$ and $N_3$. We analyze the simplest case
of two-level $N_1-N_2$ leptogenesis, including significant mass hierarchies, in
which the $CP$ asymmetry is generated in part by singlet-mediated decays of
$N_2$. For these models, provided the lightest singlet neutrino $N_1$ is
sufficiently weakly coupled to avoid excessive washout, its mass scale is not
directly constrained by the Davidson-Ibarra bound.
