Electricity transmission system is well recognized as a lifeline system in the modern society, and its failures in past major earthquakes have aroused the concern about its seismic vulnerability. In the present study, fragility curves are developed to assess the vulnerability of a typical transmission tower subjected to near-field ground motions. A probabilistic seismic demand model (PSDM) is constructed for the transmission tower in terms of the maximum inter-segment drift ratio (ISDR) and the spectral acceleration (Sa) at the fundamental period of the structure. Pushover analysis is performed to define the capacity limit states for the transmission tower, which are serviceability, damage control and collapse prevention in this research. The data for the PSDM are acquired by using incremental dynamic analyses (IDAs) of a suite of seismic records. Additionally, the influence of the seismic incident angles and the coupling effect between the transmission tower and lines on the structural fragility are further investigated. The results quantify the seismic vulnerability of the transmission tower and demonstrate the influence of the seismic incident angles and the dynamic coupling effect between the transmission tower and lines. •A new probabilistic seismic demand model is constructed for the transmission tower•Fragility curves are developed for the transmission tower subjected to near-field ground motions•Influence of the seismic incident angles and the dynamic coupling effect on the structural fragility are investigated.