This paper theoretically analyzes the flow formation and heat transfer characteristics of fully developed natural convection flow in a vertical tube due to time periodic heating of the surface of the tube. The mathematical model responsible for the present physical situation is presented under relevant boundary conditions. The essential features of natural convection flow formation and associated heat transfer characteristics through the vertical tube are clearly highlighted by the variation in the dimensionless velocity, dimensionless temperature, skin-friction, mass flow rate and rate of heat transfer. Moreover, the effect of Prandtl number and Strouhal number on the momentum and thermal transport characteristics is discussed thoroughly. The study reveals that flow formation, rate of heat transfer and mass flow rate are appreciably influenced by Prandtl number and Strouhal number.