A fully reconstructed ${B}_{c}\ensuremath{\rightarrow}J/\ensuremath{\psi}\ensuremath{\pi}$ signal is observed with the D0 detector at the Fermilab Tevatron $p\overline{p}$ collider using $1.3\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$ of integrated luminosity. The signal consists of $54\ifmmode\pm\else\textpm\fi{}12$ candidates with a significance that exceeds 5 standard deviations, and confirms earlier observations of this decay. The measured mass of the ${B}_{c}$ meson is $6300\ifmmode\pm\else\textpm\fi{}14(\mathrm{stat})\ifmmode\pm\else\textpm\fi{}5(\mathrm{syst})\text{ }\text{ }\mathrm{MeV}/{c}^{2}$.