Earthquakes, such as the 1999 Chi-Chi earthquake and the 2008 Wenchuan earthquake and many more, have caused varying degrees of damage to rock tunnels. One of the primary causes of seismic damage to these tunnels is poor ground conditions. Therefore, it is essential to study and understand the ground conditions of rock tunnels during earthquakes, as well as to collect geological and ground-related data from damaged tunnel sites. As a result, data related to rock mass has been collected from 235 tunnel sites that were damaged by 26 different earthquakes worldwide. This study highlights rock mass conditions of those seismically damaged tunnels. This study identifies the Rock Mass Rating (RMR) system as a critical factor. A clear pattern has been identified between Rock Mass Rating (RMR) and the extent of seismic damage in rock tunnels. Utilizing these observations, two cases of seismically damaged tunnels are discussed, affected by the 2022 Menyuan earthquake (Mw 6.6) in China and the 2023 Pazarick (Mw 7.8) and Elbistan (Mw 7.6) earthquakes in Türkiye, along with their rock mass conditions. While several parameters contribute to seismic damage in tunnels, this study specifically focuses on the influence of rock mass conditions. This study enhances our understanding of rock mass conditions in tunnels residing in seismic regions.