Altered cognitive function can be a distressing side effect of cancer and its treatment. Women diagnosed and treated for breast cancer often report problems with memory, concentration, and other cognitive abilities that can pose significant barriers to full resumption of family, job, and social roles. Despite considerable neuropsychological research, many unanswered questions remain about cancer-related cognitive deficits and the underlying neural bases. Functional magnetic resonance imaging (fMRI) measures brain activation associated with different mental states and has significantly advanced our understanding of cognitive function and dysfunction in healthy and clinical populations. However, to date the application of fMRI to the study of cognitive function in breast cancer is limited. The current review addresses the potential importance of this method for understanding the neurocognitive effects of breast cancer disease and treatment. Along with reviewing published fMRI studies on breast cancer to date, we discuss potential major contributions of this method which include: (a) delineating components of cognitive function and underlying neural processes most affected by cancer and its treatment, (b) uncovering compensatory processes and their limits, (c) identifying altered resting state networks that may relate to subjective complaints and longer term outcomes, and (d) clarifying the relationship between pre-treatment alterations in brain activity and longer term neural and behavioral outcomes. Finally, we pose questions for future research that can be optimally addressed by integrating fMRI and other imaging modalities to clarify the nature and causes of "chemo brain" and guide interventions to improve cognitive function and the quality of breast cancer survivorship.