The current study aims to determine the dynamic vibration characteristics and structural earthquake performance of the approach viaducts of Bosphorus Suspension Bridge. Ortakoy viaduct at European continent and Beylerbeyi viaduct at Asian continent have a length of 231 and 235 m, and five spans and four spans, respectively. The viaducts are side span of the bridge and are supported at the base instead of hanger elements. Based on the project specifications of the viaducts, 3-D detailed finite element model of the viaducts is developed by the use of frame-elements, and natural frequencies and corresponding mode shapes of the viaducts are presented in the study. Paying attention to these considerations, pushover (POA) and nonlinear time-history analysis (NTHA) are performed to attain structural-earthquake performance of the viaducts according to Turkish code for the earthquake design of railways bridges (TSC-R/2008) and Caltrans (CALTRANS-2001) seismic design of steel bridge. Accordingly, the earthquake performance of the bridge is presented for each non-linear analysis method considering these codes.