  Supernova remnants (SNRs) are strong thermal emitters of infrared radiation.
The most prominent lines in the near-infrared spectra of SNRs are [Fe II]
lines. The [Fe II] lines are from shocked dense atomic gases, so they trace
SNRs in dense environments. After briefly reviewing the physics of the [Fe II]
emission in SNR shocks, I describe the observational results which show that
there are two groups of SNRs bright in [Fe II] emission: middle-aged SNRs
interacting with molecular clouds and young core-collapse SNRs in dense
circumstellar medium. The SNRs belonging to the former group are also bright in
near-infrared H$_2$ emission, indicating that both atomic and molecular shocks
are pervasive in these SNRs. The SNRs belonging to the latter group have
relatively small radii in general, implying that most of them are likely the
remnants of SN IIL/b or SN IIn that had strong mass loss before the explosion.
I also comment on the "[Fe II]-H$_2$ reversal" in SNRs and on using the [Fe
II]-line luminosity as an indicator of the supernova (SN) rate in galaxies. In
the mid- and far-infrared regimes, thermal dust emission is dominant. The dust
in SNRs can be heated either by collisions with gas species in a hot plasma or
by radiation from a shock front. I discuss the characteristics of the infrared
morphology of the SNRs interacting with molecular clouds and their dust heating
processes. Finally, I give a brief summary of the detection of SN dust and
crystalline silicate dust in SNRs.
