Compared to White Americans, African-Americans are less likely to use primary care (PC) as their usual source of care. This is generally attributed to race differences in socioeconomic status and in access to primary care services. Little is known about the relationship between race differences in medical mistrust and the usual source of care disparity. Using data from the Exploring Health Disparities in Integrated Communities (EHDIC) study, we examined the role of medical mistrust in choosing usual source of care in 1408 black and white adults who were exposed to the same healthcare facilities and low-income racially integrated community. Multinomial logistic regression models were estimated to examine the relationship between race, medical mistrust, and usual source of care. After adjusting for demographic and health-related factors, African-Americans were more likely than whites to use the emergency department (ED) (relative risk ratio [RRR] = 1.43 (95 % confidence interval (CI) [1.06-1.94])) and hospital outpatient department (RRR1.50 (95 %CI [1.10-2.05])) versus primary care as a usual source of care. When medical mistrust was added to the model, the gap between African-Americans' and whites' risk of using the ED versus primary care as a usual source of care closed (RRR = 1.29; 95 % CI [0.91-1.83]). However, race differences in the use of the hospital outpatient department remained even after accounting for medical mistrust (RRR = 1.67; 95 % CI [1.16-2.40]). Accounting for medical mistrust eliminated the ED-as-usual-source of care disparity. This study highlights the importance of medical mistrust as an intervention point for decreasing ED use as a usual source of care by low-income, urban African-Americans.