Background Patient navigation (PN) is an emerging strategy to overcome barriers to cancer care. We evaluated the efficacy of PN in improving time of key events in cancer care, including positive screening tests, definitive diagnosis, initiation of therapy, and completion of initial therapy. Methods We evaluated PN in a prospective observational study of predominantly poor Hispanic women with an abnormal breast cancer screening or untreated biopsy proven breast cancer (control = 200, intervention = 260). Controls were contemporary records-based patients with positive screening. Analyses were conducted for the entire cohort and separately by ethnic strata. We used Chi-Square tests to compare differences in proportions and Kaplan-Meier followed by Cox Regression to compare time-to-event curves of the intervention and control groups. Results The average days from definitive diagnosis to initiation of therapy was significantly reduced overall with PN (PN vs control, 57d vs 74d, p=.04). This effect was more pronounced in the Hispanic strata (56 vs 81 days, p=.02). More navigated Hispanic women were diagnosed within 60 days of abnormal screening (62.6% vs 47.5%, p< .01) and more began treatment within 60 days of diagnosis (80% vs 56.3%, p<.01). Navigated Hispanic and other ethnic minority women had a shorter time from positive screening test to definitive diagnosis (16 and 32 days, respectively). Conclusions Minority women may have benefitted from navigation with shorter times from definitive diagnosis to initiation of therapy.. Impact PN intervention may show promise in decreasing some delays that contribute to health disparities among minority women with breast cancer.