The goal of this study was to find predictors of the mental health status of the fourth batch of Indonesian candidates coming to Japan under the Japan–Indonesia Economic Partnership Agreement, 4 months after the Great East Japan Earthquake. A four-page-long questionnaire was developed and distributed to the fourth batch of Indonesian candidates, who wished to go to Japan under the above agreement, at the venue of an intensive Japanese language course held in Depok, West Java, Indonesia, in July 2011. Seventy-six percent of the respondents were female. The average age was 24.7 (standard deviation [SD] 2.8) years old. Forty-nine percent of the respondents answered that they were very worried or somewhat worried about the aftermath of the Great East Japan Earthquake. The mean Score of Knowledge about Japan, including knowledge about the working and living environments in Japan, was 53.3 and ranged from 20 to 80 (SD 7.3) points. The average score of the General Health Questionnaire, which was used as a marker of the mental health status in this study, was 36.1 (SD 4.2) points. The result of a multivariate analysis showed that the Score of Knowledge about Japan was significantly correlated to the General Health Questionnaire score (β=−.234, P < 0.05), but the degree of worry about the earthquake was not. The result indicated that knowledge about the actual living and working conditions in Japan is a major indicator of the mental health of the candidates, but not their worry concerning the earthquake.