  We study the exclusive semi-tauonic B decay, $\bar B \to D \tau
\bar\nu_{\tau}$, in two-Higgs-doublet models. Using recent experimental and
theoretical results on hadronic form factors, we estimate theoretical
uncertainties in the branching ratio. As a result, we clarify the potential
sensitivity of this mode to the charged Higgs exchange. Our analysis will help
to probe the charged Higgs boson at present and future B factory experiments.
