In the heating of a cylindrical laminar liquid jet or a droplet by the condensation of the saturated vapor, the effects of the condensed film have been analysed. Theoretical solutions have been derived to evaluate the non-dimensional average temperature and Nusselt number in the heating of a cylindrical liquid jet or a droplet, separately. Based on the theoretical solutions in the heating of a cylindrical liquid jet, the effects of the dominant parameters, such as the ratio of thermal conductivity of the condensed liquid film to that of the liquid jet, Jacob number of the vapor and the ratio of heat capacity of the condensed liquid film in unit volume to that of the liquid jet, are discussed. It is found that the effects of the condensed liquid film in the heating of a cylindrical liquid jet or a droplet by the condensation of the vapor are more important in the case of smaller Graetz number or larger Fourier number. Approximate solutions to estimate the non-dimensional temperature and Nusselt number have been also derived for the case of smaller or larger Graetz (Fourier) number. Relative accuracies and effectiveness of the approximate solutions for a cylindrical liquid jet are discussed in the present paper.