Personality is the man. The successful living of an individual, as a man, depends to a large extent on the academic achievement of that individual, as a student. This article attempts to find out personality type, academic achievement of secondary school students and relationship between them by selecting a sample of 300 secondary school students from Tirunelveli. Survey method was used. The collected data, using Multidimensional Personality Inventory and quarterly examination marks were analyzed statistically and the results show that the personality type of secondary students is ambient, their academic achievement is average and there exists relationship between personality type and academic achievement of secondary school students with reference to some factors and there is no relationship with regard to some other variables, suggesting that there could be some other factors that influence their academic achievement.