This study examines the relationship between career interests, aptitude, mental health, happiness and academic performance among first-year high school students. The proposed study performs a descriptive research on 370 first-year students using multistage random cluster survey to collect the necessary data. The proposed study also uses strong career interest questionnaires, Oxford Happiness test, Health and Aptitude test scores and the semester GPA scores. Research data are analyzed by Pearson correlation coefficient, and stepwise regression procedures. The results indicate that there is a significant and direct relationship between realistic, investigative, artistic, social, enterprising, convention and academic performance; but there is an unusual and significant inverse relation between realistic and academic performance. In addition, there is a direct relationship between mental health and academic performance, and between aptitude, happiness and academic performance. Generally, there is a relationship between career interest, aptitude, mental health, happiness and academic performance; and the greatest impact on academic performance is related to career interest, particularly investigative interest.