Purpose: To assess metastatic breast cancer (MBC) patient perceptions and comprehension of tumor genomic testing and to evaluate associations with psychological wellbeing. Methods: In a prospective, single institution, single-arm trial, patients with MBC underwent next-generation sequencing at study entry, with sequencing results released at progression. Patients who completed surveys before undergoing sequencing were included in the study (n=58). We administered four validated psychosocial measures: Center for Epidemiologic Studies Depression Scale, Beck Anxiety Inventory, Trust in Physician Scale, and Communication and Attitudinal Self-Efficacy scale for Cancer. Genetic comprehension was assessed using 7-question objective and 6-question subjective measures. Longitudinal data were assessed using paired Wilcoxon signed rank and McNemar’s test of agreement. Results: There were no significant differences between the beginning and end of study in depression, anxiety, physician trust, or self-efficacy (median time on study: 7.6 months). Depression and anxiety were positively associated with each other and both negatively associated with self-efficacy. Self-efficacy decreased from pre- to post-genomic testing (p=0.05). There was a wide range of objective genetics comprehension and comprehension was significantly lower in non-white patients (p=0.02) and patients with lower income (p=0.04). Patients expressed increased confidence in their ability to teach others about genetics at end of study. Conclusions: This is the only study, to our knowledge, to longitudinally evaluate multiple psychological metrics in MBC as patients undergo tumor genomic testing. Among patients with MBC, depression and anxiety metrics were negatively correlated with patient self-efficacy. Patients undergoing somatic genomic testing had limited genomic knowledge, which varied by demographic groups.