We have investigated the thermal effects on the properties of open heavy-flavor mesons using a unitarized effective hadronic theory in coupled channels based on chiral and heavy-quark symmetries at finite temperature below Tc within the imaginary-time formalism. The in-medium amplitudes of the scattering of the heavy mesons with the light mesons and the ground-state self-energies and spectral functions are calculated in a self-consistent manner. I will present our findings for the thermal masses and widths of the open heavy-flavor ground states, as well as for the dynamically generated states . I will also show our results for the meson Euclidean correlators obtained from the thermal spectral functions and their comparison with lattice QCD simulations . In addition I will show our recent calculations of transport coefficients below Tc .