BACKGROUND: The Fukushima Nuclear Energy Workers' Support study showed the Fukushima nuclear disaster caused psychological distress in the workers, with higher rates of post-traumatic stress responses (PTSR). To understand how the type and duration of emergency recovery work performed immediately following this disaster impacted workers' psychological status, a longitudinal analysis was conducted with 4-year follow-up data since 2011. METHOD: Fukushima Daiichi nuclear power plant workers were assessed annually with general psychological distress (GPD) and PTSR questionnaires between 2011 and 2014. Combined, 697 Fukushima Daiichi plant workers provided baseline GPD and PTSR in 2011 and their record of working days for approximately one month immediately following the disaster. The relationship between type of emergency recovery work, working days immediately following the disaster, and psychological distress over four years was analyzed using a mixed effects logistic regression model. RESULTS: At baseline, GPD and PTSR scores were significantly higher in nuclear power plant workers who worked 3-5 days immediately following the disaster compared to those who worked only 0-2, particularly in the field engineer subgroup. The effect of working days on GPD remained for over a year, and the impact on PTSR remained significant throughout the four years of observation after the disaster. CONCLUSIONS: The Fukushima Daiichi plant field engineers showed significantly higher psychological distress than other workers. The impact of emergency recovery work on psychological distress persisted for over one year, but PTSR in field engineer workers remained significantly elevated four years after the disaster.