Interference processing requires increased focus on relevant dimensions of environmental stimuli and selective allocation of attentional resources, in order to filter extraneous information and inhibit non-adaptive responses. This process is important in everyday life and is necessary for responding to novel and challenging situations. Dorsal anterior cingulate cortex (dACC) is involved in this process, and behavioral twin studies indicate that performance on interference processing tasks is highly heritable. However, the extent to which dACC activation related to such tasks is influenced by genetic factors has not been reported. In the current study, 10 pairs of monozygotic and 10 pairs of dizygotic female twins performed a validated interference processing task during fMRI. There were three main results: (1) increased dACC activation for incongruent (INC) minus congruent (CON) trials was observed; (2) dACC activation for INC minus CON trials was both moderately heritable and significantly correlated with the difference in reaction time (RT) between INC and CON trials; (3) RT for INC trials was moderately heritable. RT for CON trials and the latency difference between INC and CON trials were not influenced significantly by genetic factors. The current study provides the first functional imaging evidence that dACC activation during interference processing is significantly influenced by genes. These results suggest an endophenotype that may be applied to various psychiatric disorders that are both highly heritable and associated with altered dACC function.