In the article, on the background of theoretical considerations on the meaning of the sense of self-efficacy in the work of a modern teacher functioning in the changing conditions of the 21st century reality and the role that personality (in terms of the Five-Factor Theory of Personality by Paul T. Costa and Robert R. McCrae) may play in shaping this key factor, the results of empirical research conducted with the participation of Polish and American teachers are presented. The analyzes proved that the respondents who were characterized by a statistically significantly higher level of self-efficacy were also characterized by such an intensity of personality traits in terms of the Big Five (neuroticism, extraversion, openness to experience, agreeableness and conscientiousness), which corresponded to the pattern of teacher personality, which has been present in the pedeutological discourse over the years.