We study the exclusive semi-tauonic B decay, $bar B to D tau bar u_{tau}$, 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.