Background: Both comorbidities and obesity (body mass index/BMI 30 or higher) are observed in women at the time of early breast cancer (EBC) diagnosis. This study investigates age and obesity and their association with disparities in comorbidities between black and white women at EBC diagnosis. Methods: This is a retrospective chart review of women with EBC (Stage I-III) treated at a single institution. Relative risk (RR) with 95% Confidence Interval (CI) for individual comorbidities are calculated for black compared to white patients, adjusted for age and BMI. Results: In a sample of 548 women, 26% are black and 74% are white. 18% of black patients vs 28% of white patients were age 65 or older (p = .01). 62% of black vs 33% of white patients had obesity (p < .0001). 63% of black vs 47% of white patients had 2 or more total comorbidities at diagnosis (p = .003). 33% of black vs 10% of white patients had 2 or more obesity-related comorbidities (p < .0001). 60% of black vs 32% of white patients had hypertension (p < .0001); 23% of black vs 6% of white patients had diabetes (p < .0001); and 28% of black vs 18% of white patients had high cholesterol (p = .02). In multivariable (MV) analysis adjusted for age and BMI, black women had 45% higher risk for hypertension [RR 1.45 (1.19-1.75), p = .0002)] and 44% higher risk for diabetes [RR 1.44 (1.02-5.86), p < .0001)] at EBC diagnosis. However, after adjustment, differences by race were no longer seen for > = 2 total comorbidities, > = 2 obesity-related comorbidities, heart disease, or thyroid disease. Conclusions: This study documents significant disparities between black and white women with EBC with regard to high rates of obesity, overall comorbidities and obesity-related comorbidities. Future research should assess the potential impact of weight management (avoiding weight gain) interventions in the first 2 years post diagnosis on improving OS and BCSS among patients with obesity and in reducing OS and BCSS disparities between black and white women.