This study investigated nursing students' major satisfaction and self-efficacy in relation to career preparation activities during high school. Career preparation activities included career education, counseling, club activities, and volunteer activities. The subjects were 246 nursing students from G and C Province and Seoul. The data were collected from 10 July to 16 August 2018 using a structured questionnaire. SPSS 21.0 program was used for data analysis with frequency and percentage, t-test, ANOVA, and Scheffé test. The results showed that there were significant differences in major satisfaction and self-efficacy according to subjects' age, gender, and grade. Subjects who had chosen their major themselves or who had experienced career education and guidance during high school also had higher levels of major satisfaction and self-efficacy. Subjects who participated in club activities during high school showed higher self-efficacy, and subjects who performed volunteer activities showed higher satisfaction with their major. In conclusion, since various career preparation activities during high school seem to be closely related to major contentment and self-efficacy among nursing students, it would be necessary to allow high school students to explore their interested major in a variety of ways, including education, counseling, club activities, and volunteer work.