Breast cancer in women between the ages of 15 and 39 years (adolescents and young adults [AYAs]) constitutes 5% to 6% of all breast cancer cases in the United States. Breast cancer in AYA women has a worse prognosis than in older women. Five-year survival rates are lowest for AYA women, and only a few studies have examined the impact of delay in treatment, race/ethnicity, and other socioeconomic factors on survival in AYA women. To examine the impact of treatment delay time (TDT), race/ethnicity, socioeconomic status, insurance status, cancer stage, and age on the survival from breast cancer among AYA women. This is a retrospective case-only study of 8860 AYA breast cancer cases diagnosed from 1997 to 2006 using the California Cancer Registry database. Treatment delay time was defined as the number of weeks between the date of diagnosis and date of definitive treatment. Kaplan-Meier estimation was used to generate survival curves, and a multivariate Cox proportional hazards regression model was performed to assess the association of TDT with survival while accounting for covariates (age, race/ethnicity, socioeconomic status, insurance status, cancer stage [American Joint Committee on Cancer], tumor markers, and treatment). Five-year survival rates for breast cancer as influenced by host factors, tumor factors, and TDT. Treatment delay time more than 6 weeks after diagnosis was significantly different (P < .001) between racial/ethnic groups (Hispanic, 15.3% and African American, 15.3% compared with non-Hispanic white, 8.1%). Women with public or no insurance (17.8%) compared with those with private insurance (9.5%) and women with low socioeconomic status (17.5%) compared with those with high socioeconomic status (7.7%) were shown to have TDT more than 6 weeks. The 5-year survival in women who were treated by surgery and had TDT more than 6 weeks was 80% compared with 90% (P = .005) in those with TDT less than 2 weeks. In multivariate analysis, longer TDT, estrogen receptor negative status, having public or no insurance, and late cancer stage were significant risk factors for shorter survival. AND RELEVANCE: Young women with breast cancer with a longer TDT have significantly decreased survival time compared with those with a shorter TDT. This adverse impact on survival was more pronounced in African American women, those with public or no insurance, and those with low SES.