Thermal behavior of optical fiber during the cooling stage of drawing process has been studied numerically. An optical fiber during the cooling stage of drawing process has been modeled as finite-length of the cylinder moving in still air at a constant drawing speed. A two-dimensional unsteady-state energy equation is solved using finite difference schemes. Two-dimensional steady-state boundary layer equations are solved using implicit finite difference method to estimate a convective heat transfer coefficient of air at the surface of fiber. The effects of drawing speed, diameter and fiber material on cooling rate of optical fiber are reported here. The average convective heat transfer coefficient of air around the surface of fiber has been estimated accurately and validated with the experimental results available in the literature. Results have shown that there is an increase in cooling rate of optical fiber with increase in drawing speed. The size of fiber has shown a significant effect on cooling rate of fiber at low drawing speeds. Present results are matching well with the analytical and experimental results available in the literature. © IMechE 2014.