This paper presents the methodology, technology, and special considerations that were applied in the seismic stress test of Koeberg Nuclear Power Plant in South Africa. This seismic stress test was undertaken in response to the events at Fukushima Daiichi on 11 March 2011 and was set with a review level earthquake of 0.5g zero period ground acceleration. Special considerations that had to be taken into account during the assessment included that the nuclear island of Koeberg is seismically isolated.