The seismic vulnerability of bridges may be reduced by the application of Geotechnical Seismic Isolation (GSI) below the foundations of the columns and the abutments. However, the role of GSI on the seismic response of bridges has been limitedly examined in literature. Therefore, this research has been conducted to study the effect of applying GSI on the seismic response of bridges to address the aforementioned gap in knowledge. Advanced nonlinear dynamic three-dimensional finite element analyses have been conducted using OpenSees to study the influence of the GSI. The cases of traditional and isolated bridges subjected to earthquakes have been considered to assess the GSI effects. The results showed that the GSI reduces the seismic effect on the column while its effect seems to be less significant for the abutments. In addition, fragility curves for the traditional and isolated cases have been developed and compared to provide insights with a probabilistic-based approach. The results of this paper provide a useful benchmark for design considerations regarding the use of GSI for bridges.