Self-esteem develops and evolves throughout our lives as we build an image of ourselves through our experiences with different people and activities. Experiences during our childhood play a particularly large role in shaping our basic Self-esteem. Many of the circumstances that affect a child’s Self-esteem arise in connection with his life at school. The degree of child’s self-esteem which will be influenced by his success or failure in the school situation will also be determined by the extent to which the child feels about his personal worth and about his achievement. The attempt made by the present study is to probe the relationship of self-esteem and achievement of secondary school students and to fill a gap in the existing literature on the subject. A sample of 300 students were selected from management and Government school high schools using purposive sampling technique. The tools used are Self Esteem Inventory developed by S. Karunanidhi (1996) and Achievement score obtained from schools by students. It is found that there is a medium level of Self esteem and Academic Achievement among high school students. There is a significant relationship between self esteem and academic achievement in mathematics. There is no significant difference between boys and girls, management and Govt. school students and rural and urban school students with respect to self esteem and academic achievement.