Chimneys are usually subject to severe environmental conditions such as chemical attacks and extreme heat or cold. In addition, they are often subjected to operating conditions that change over time. Chimneys begin to deteriorate from the moment they are built, even before being put into service. As a result, many existing chimneys may require repair and strengthening after few years of operation. This paper describes how externally bonded fiber-reinforced polymer (FRP) reinforcement was used to increase the seismic resistance of an existing 140 m tall reinforced concrete (RC) chimney located in a power plant in Arkansas, United States. Design of the FRP reinforcement for this project was based on combining the design principles of ACI 440.2R and ACI 307 to develop an iterative design procedure. The design method, utilizing the concepts of strain compatibility and force equilibrium, allows for the determining the flexural capacity of chimney with and without openings. Chimney strengthening was achieved using vertical carbon FRP strips bonded to the inside and outside faces of the chimney. At the base of the chimney, strengthening was achieved using a combination of externally bonded FRP and concrete section enlargement.