While not itself life-threatening, ductal carcinoma in situ (DCIS) can progress to invasive disease if untreated, and confers an increased risk of future breast cancer. We investigated knowledge of DCIS among a cohort of English- and Spanish-speaking Latina and English-speaking non-Latina white women previously treated for DCIS. We examined knowledge of DCIS with four true/false statements about risk of invasive disease, breast cancer recurrence, and prognosis. For each knowledge statement, we modeled the odds of a correct answer by language-ethnicity (English-speaking Latinas, Spanish-speaking Latinas, and English-speaking whites) adjusting for demographics, health history, and treatment factors. Of 710 participants, 52 % were English-speaking whites, 21 % English-speaking Latinas, and 27 % Spanish-speaking Latinas. Less than half (41 %) of participants were aware that DCIS is not life-threatening and only 32 % knew that surgical treatment choice does not impact mortality; whereas two-thirds (67 %) understood that DCIS confers increased risk of future breast cancer, and almost all (92 %) knew that DCIS, if untreated, could become invasive. Only three Spanish-speakers used professional interpreters during discussions with their physicians. In adjusted analyses, compared to English-speaking whites, both English- and Spanish-speaking Latinas had significantly lower odds of knowing that DCIS was not life-threatening (OR, 95 % CI 0.6, 0.4-0.9 and 0.5, 0.3-0.9, respectively). In contrast, Spanish-speaking Latinas had a twofold higher odds of knowing that DCIS increases risk of future breast cancer (OR, 95 % CI 2.6, 1.6-4.4), but English-speaking Latinas were no different from English-speaking whites. Our data suggest that physicians are more successful at conveying the risks conferred by DCIS than the nuances of DCIS as a non-life-threatening diagnosis. This uneven communication is most marked for Spanish-speaking Latinas. In addition to the use of professional interpreters, efforts to create culturally and linguistically standardized information could improve knowledge and engagement in informed decision making for all DCIS patients.