Probabilistic safety assessment (PSA) is considered to be an important tool for assessing the safety of nuclear installations (typically used for safety assessment of nuclear power plants) in relation to potential initiating events that can be caused by random component failure and human error, as well as internal and external hazards. The purpose of seismic PSAs performed on nuclear installations is to provide risk insights related to their seismic robustness. The methodology for seismic safety evaluations includes a combination of deterministic and probabilistic approaches. Their applications typically address the impact of beyond design basis seismic events. This publication provides a detailed methodology for seismic PSA in line with the current international practices for seismic safety assessment of nuclear installations. Taking into account recommendations provided in IAEA safety standards and information reflected in internationally recognized technical standards, it reflects the current state of practice in the area of seismic PSA.