Because transmission tower-line systems are always exposed to the natural environment, such structures are vulnerable to various meteorological conditions, and the rupture of a transmission line is a particularly serious potential accident. Although many studies have been conducted on the dynamic responses of transmission towers subjected to cable rupture, few have considered the uncertainties that exist in the structures of transmission towers. To investigate the effects of the uncertainties in material properties and geometric parameters on the dynamic responses caused by cable rupture, a finite-element (FE) model is established in Abaqus; then deterministic, sensitivity, and probability analyses are conducted in succession. This study reveals that the yield strength and geometric size of diagonal members have significant effects on the responses of a transmission tower subjected to conductor rupture. In addition, based on the probability analysis, the results of the deterministic analysis are reliable, and structures under a conductor rupture load have a substantial probability of being partially damaged, which means that current design codes must be improved.