  We calculate the anomalous magnetic moment of the electron in the
Chern-Simons theory in 2+1 dimensions with and without a Maxwell term, both at
zero temperature as well as at finite temperature. In the case of the
Maxwell-Chern-Simons (MCS) theory, we find that there is an infrared
divergence, both at zero as well as at finite temperature, when the tree level
Chern-Simons term vanishes, which suggests that a Chern-Simons term is
essential in such theories. At high temperature, the thermal correction in the
MCS theory behaves as $\frac{1}{\beta} \ln \beta M$, where $\beta$ denotes the
inverse temperature and $M$, the Chern-Simons coefficient. On the other hand,
we find no thermal correction to the anomalous magnetic moment in the pure
Chern-Simons (CS) theory.
