Objective To determine the association of age at index birth with postpartum contraceptive use and optimal interpregnancy interval (IPI, defined as delivery to next pregnancy >18 months), controlling for provider type and client demographics among adolescent mothers who have repeat pregnancies. Methods California's 2008 birth records were linked to California's Medi-Cal and Family PACT claims data to identify 26,393 women with repeat births between 2002 and 2008, whose index birth occurred as an adolescent, and who received publicly-funded services within 18 months after the index birth. Multivariable regression analyses were conducted to examine the relationship between timing of contraception provision and interpregnancy intervals, adjusting for socio-demographic factors. Results Seventy-eight percent of adolescent women did not receive contraception at their first postpartum visit, and twenty-eight percent of adolescent women never received contraception from a Family PACT or Medi-Cal provider. Adolescents who were older at their index birth had lower rates of optimal IPIs. Native American, Asian-Pacific Islander and Latina women had lower rates of optimal IPIs compared to white women. Compared to those using only barrier methods, adolescent women receiving highly effective contraceptive methods had a 4.25 times higher odds of having an optimal IPI than those receiving hormonal methods (OR 2.10), or using no method (OR 0.70). Conclusion Effective postpartum contraceptive use and being a Family PACT provider were associated with optimal birth spacing among adolescent mothers, yet racial and ethnic disparities persisted. A missed opportunity was the provision of contraception at the first postpartum visit. Providers should aim to remove barriers to initiation of contraception at this visit.