The fertility rate (TFR) has decreased from around 5.6 births per woman in 1967 to around 2.4 births today. This study examined the desired number of children and related factors among adolescents in Indonesia in order to clarify expected fertility behavior. This study employed the data from a national survey of National Medium Term Development Plan 2015 (RPJMN 2015). This paper involved unmarried adolescences aged 15-24. The selected respondents were 37,538 persons. The multiple linear regression was applied to predict the model. The result showed that the majority of respondents were female, aged 15-16 years old, mostly senior high school level, had been out of school, unemployed, and lived in rural areas of Java, Bali and Sumatra. The average desired number of children was 2.46, with a 0.86 standard deviation. The multiple linear regression showed that sex, age, education level, working status, contraceptive knowledge, and living in rural and various regions significantly influenced the number of expected children. In conclusion, the majority of respondents expressed their desire to have only one or two children in the future. However, in consideration of the fact that what one desires does not always reflect reality, the risk of falling fertility is generally present. Policymakers on family planning need to be aware of this issue and should identify key issues in childbirth policy to support families in having a reasonable amount of children.