The electric power transmission network is a crucial lifeline in modern society, and it needs to be protected against extreme loading conditions such as in an earthquake. The seismic fragility curves of high voltage transmission towers in South Korea are developed based on the limit states that are defined in terms of yielding and buckling of the structural members of the towers. The finite element models of the representative transmission towers in South Korea are developed based on the assumption of linear elastic behavior, and a series of time history analyses are performed using a set of 20 recorded ground motions. The maximum likelihood estimation method is used to develop fragility curves from numerous simulations. It is concluded that the transmission towers are safe under a design level earthquake in South Korea. When a strong earthquake occurs, buckling of the members is more likely to occur before yielding in the axial direction in the case of the 765 kV and 345 kV transmission towers, while the opposite is observed for the 154 kV transmission tower.