Abstract: The objective of this study is to establish the relationship that exists between timing of first childbirth and level of child fostering in Southwestern, Nigeria. Quantitative research method which involves multi-stage random sampling of 1,000 women of reproductive age (15-49 years) with at least a live birth was used in the study. In addition, 10 in-depth interviews were conducted among the populace in the study area. The pre-childbirth family socio-economic backgrounds of respondents for survey were controlled and all the respondents had similar pre-childbirth socio-economic background. The only discriminatory variable that separates these respondents into 2 groups is the timing of the first childbirth. The study group consists of 500 adolescent mothers who had their first childbirths during ages 10-19 years; while the control group consists of 500 older mothers that had their first childbirths at age 20 years and above. Findings of the study show significant relationship between age at first childbirth and level of child fostering at p<0.01. Specifically, 40.8% of adolescent mothers compared with 9.8% of older mothers have fostered at least one of their children. Findings on socio-economic differentials in the level of child fostering show significant relationships between place of residence, current age, educational level, occupational status, marital status, form of marriage, number of children ever and level of child fostering. For example, there is significant difference in level of child fostering between adolescent mothers in the rural and urban areas of the region at F = 4.2, p<0.05. In conclusion, women who have their first childbirth as adolescents, irrespective of their socio-economic status, are more likely to foster their children than those who delay childbearing until their twenties, when the later were at similar categories to the former, in the region.