The heat transfer from circular cylinders in turbulent cross flows plays a significant role in industrial operations. The objective of this paper is to evaluate the heat transfer from a cylinder with circular cross section and four flexible fins in turbulent flows numerically. The governing equations of thermal fluid are discretized by finite element method (FEM) while the equations of motion of deformable structure of fins are discretized by finite element method (FEM). The k-ω SST model is used to simulate the flow. The results are validated by comparing the heat transfer rate from the circular cylinder with that of other investigators’ experimental and numerical studies. In addition, the fluid-structure interaction (FSI) results are validated against a benchmark example. The flexible fins are glued to the circular cylinder by two different angles (θ=0° and θ=45°). In both cases, the thermal enhancement, as well as the flow-induced vibrations of the fins, are investigated for various non-dimensional flexural rigidity. It is found that attached fins in both angles and the flexural rigidity are significantly affect Nusselt number. Moreover, it is found that the very flexible fins can increase the Nusselt number by 26%.