Background: Roma (Gypsies) constitute one of the largest ethnic minorities in Slovakia. Some reports have supported a higher prevalence of communicable diseases in Roma but data on cancer prevalence in Roma is absent. The aim of this study was to compare differences in the incidence and pathological characteristics of breast cancer between Roma and non-Roma in Slovakia. Patients and Methods: Roma and non-Roma breast cancer patients were identified using the Slovak HER2 Registry. The database from the last Census of Slovakia in 2011 was matched by gender, date of birth, and residency with the HER2 Registry from 2011 to 2013. Based on the match, Roma and non-Roma breast cancer patients were identified. Results: Thirty-two and 5,775 women with breast cancer were identified as Roma and non-Roma, resp. The age-standardized breast cancer incidence rate was 2.12 times higher for non-Roma than for Roma patients (36 vs. 17 per 100,000 people). Roma patients were younger than non-Roma patients (median 49 vs. 61 years; p = 0.00001). Roma patients had more hormone receptor negative (34.4% vs. 18.1%; p = 0.03) and triple negative tumors (28.1% vs. 12.3%; p = 0.01) than non-Roma, and these differences remained statistically significant in multivariate analysis. Conclusion: For the first time, this study has revealed that the incidence and biological characteristics of breast cancer are different between Roma and non-Roma. Our data suggests that Roma patients are younger at diagnosis, have a lower age-standardized breast cancer incidence rate, and have more aggressive tumors than non-Roma.