  We investigate the modification of the pion self-energy at finite temperature
due to its interaction with a low-density, isospin-symmetric nuclear medium
embedded in a constant magnetic background. To one loop, for fixed temperature
and density, we find that the pion effective mass increases with the magnetic
field. For the $\pi^{-}$, interestingly, this happens solely due to the trivial
Landau quantization shift $\sim |eB|$, since the real part of the self-energy
is negative in this case. In a scenario in which other charged particle species
are present and undergo an analogous trivial shift, the relevant behavior of
the effective mass might be determined essentially by the real part of the
self-energy. In this case, we find that the pion mass decreases by $\sim 10%$
for a magnetic field $|eB|\sim m_\pi^2$, which favors pion condensation at high
density and low temperatures.
