  We calculate contributions to the anomalous magnetic moment of the muon from
heavy neutral and charged Higgs bosons and new leptons in two Higgs doublet
models extended by vectorlike leptons. We present detailed predictions of two
models with type-II couplings to standard model fermions, motivated by a $Z_2$
symmetry and supersymmetry. In addition, we compare the results with the
standard model extended by vectorlike leptons. We find that the model motivated
by a $Z_{2}$ symmetry can generate much larger contributions to the magnetic
moment compared to the standard model, even by two orders of magnitude due to
$\tan^{2}\beta$ enhancement, while satisfying current constraints. As a
consequence, the standard model explanation of the anomaly requires much larger
corrections to muon couplings making this model easier to probe at future
precision machines. Additionally, we find that the model with couplings
motivated by supersymmetry typically leads to much smaller contributions to the
anomaly as a result of cancellations. However, we identify interesting
scenarios where contributions from the charged Higgs boson can fully explain
the anomaly.
