By applying the in viscid approximation, a simple relation for predicting the drag coefficient of a growing vapor bubble at rectilinear accelerated ascension in uniformly-superheated pure liquids was developed. The relation is valid in both regions: inertia controlled and heat diffusion controlled bubble growth, respectively. The drag coefficient decreases with time for all accelerations, as well as with augmentation of the bubble acceleration at each instant of time, independently of the internal vapor parameters.