  We propose a novel model for lepton flavor and dark matter based on the
$SU(2)_D$ gauge symmetry and vector-like leptons in its fundamental
representations. We introduce a dark $SU(2)_D$ Higgs doublet and a Higgs
bi-doublet for the mass mixing between the vector-like lepton and the lepton.
As a result, the seesaw lepton masses are generated and there are sizable
one-loop contributions to the muon $g-2$ via the $SU(2)_D$ gauge bosons and the
relatively heavy vector-like lepton, as indicated in Fermilab E989. The
tree-level mass mixing between the $Z$ boson and the isospin neutral gauge
boson of $SU(2)_D$ in our model accounts for the shift in the $W$ boson mass,
being consistent with Tevatron CDFII. Finally, we show that the isospin charged
gauge boson of $SU(2)_D$ becomes a plausible candidate for dark matter with a
small mass splitting tied up to the modified $W$ boson mass, and there is a
viable parameter space where the favored corrections to the muon $g-2$ and the
$W$ boson mass and the dark matter constraints are simultaneously fulfilled.
