Background The 2011 earthquake and tsunami in Japan caused a meltdown at the Fukushima nuclear power plant. Aims To quantify emotional responses among British nationals in Japan and to assess whether perceptions about the incident or accessing information about it were associated with responses. Method A total of 284 participants randomly selected from official records completed a survey that included instruments to measure emotional responses. Results In total, 16% met the criteria for distress, 29.7% reported high anxiety relating to the incident and 30.4% reported high anger. Perceptions that strongly predicted these outcomes included feeling uncertain, being unable to rule out harmful exposure, and believing that exposure would have severe or hidden health effects or be difficult to detect. Using information sources was associated with higher emotional outcome, particularly for sources perceived to have low credibility. Conclusions Reducing uncertainty and improving the credibility of information is essential in reducing the psychological impact of radiological disasters.