Marriage is “a process learning about one’s self and one’s spouse, about sharing, and growing up, being individuals within a family and being a member of the family team. In India adolescents girls face number of problems and are more prone for early marriage and are sexually active. Early (child) Marriage is one of the burning problems of Indian society. In India, despite amended laws advocating 21 as the legal minimum age at marriage for females, a substantial proportion i.e. every third adolescent girl in the age group of 15-19 year is married and every second married adolescent girl has given birth to a child1. Objectives: To assess the knowledge regarding effects of early marriage among adolescent girls of rural area and urban area. To compare the knowledge regarding effects of early marriage among adolescent girls (15-20 years) of rural and urban areas and to find out the association between knowledge regarding effects of early marriage among adolescent girls (15-20 years) of urban and rural area with their selected socio-demographic variables. Method: A quantitative approach, Comparative research design was adopted for this study. The sample consists of 50 adolescent girls (15-20 years) from urban and rural area. Samples were selected by using purposive sampling technique. Self structured knowledge questionnaire were used to assess the knowledge regarding effects of early marriage. Results: The result revealed that in rural area, 94% of adolescent girls had inadequate followed by 6% had moderate level of knowledge regarding effects of early marriage (1.06 ± 0.23). In urban area, 78% of adolescent had inadequate level followed by 22% had moderate level of knowledge regarding effects of early marriage (1.22 ± 0.41). Variables like education status of father, birth order in the family, mother age on marriage, type of family and area of residence were found to be statistically significant among rural adolescents i.e., p<0.05 whereas in urban area, variables like age, marital status, education status of mother, birth order in the family, working status of the mother, religion and type of family were found to be statistically significant i.e., p<0.05. Interpretation and Conclusion: Overall findings showed that there is knowledge deficit among the adolescents regarding effects of early marriage among adolescent girls.