Although research has suggested that girls in foster care are at high risk of teen birth, limited data have been available from which rates could be calculated and characterized. This California study was based on a dataset constructed by probabilistically matching foster care records to statewide birth records. Using these linked data, we computed cross-sectional birth rate estimates for 15- to 17-year-old girls who were in foster care during each year from 2006 to 2010, characterizing the placement-related experiences and timing of births. Results indicated that although only a small number of 15- to 17-year-old girls in foster care gave birth each year, their birth rate was somewhat higher than the rate observed in the general population. Girls who were in foster care for less time or experienced greater placement instability had higher rates of birth. In terms of race and ethnicity, Black and Latina adolescents in foster care were more likely to give birth than their White counterparts. During the 5-year period, there were no detectable trends in the overall birth rate of girls in foster care, despite significant declines in the birth rates of 15–17year olds in California overall. This linked data contributes new information that can be used to inform the targeting of prevention and intervention resources to girls involved with child protective services.