Background: Bilateral mastectomy improves survival for women with BRCA-associated breast cancer. Most women do not know their BRCA status at the time of BC diagnosis when making surgical decisions. Rapid genetic testing (RGT) allows a woman to have genetic test results prior to treatment decision making, but it is unclear if RGT has an impact on treatment choices. It is also unclear if there are psychosocial implications associated with genetic testing at the time of breast cancer diagnosis. The objective of the current study was to assess the impact of RGT at the time of BC diagnosis on surgical decision-making and psychosocial functioning. Methods: Eligible women were referred from participating surgeons at BC diagnosis. Women completed baseline questionnaires assessing treatment preferences, cancer related distress, anxiety, and depression. All participants received in-person pre-test genetic counselling and genetic test results were given within 10 days. Participants completed surveys at 1 week and 1 year post-genetic testing to assess treatments and psychosocial functioning. Results: 1010 women consented to participate and 60 (5.9%) were identified with a BRCA mutation. 15% of those identified with a BRCA mutation did not meet provincial eligibility criteria for genetic testing, and 20% were eligible prior to a breast cancer diagnosis but had not received testing. Mean levels of cancer-related distress, anxiety and depression declined significantly from baseline to 1 year for all women (all p < .05), and there were no differences at any time point between those with and without a BRCA mutation. Of those identified with a BRCA mutation, 67.3% reported that their surgery choice changed. 73.7% of BRCA carriers had a bilateral mastectomy, compared to 20.2% of BRCA negative (p < 0.001). Most women used genetic testing results for surgical decision making (96.1% of BRCA positive and 86.4% for negative). Conclusions: Rapid genetic testing for BRCA1 and BRCA2 at the time of BC diagnosis does not have a negative impact on psychosocial functioning. There are no differences in cancer-related distress, anxiety or depression between women who receive a positive result compare to a negative genetic test result. Furthermore, surgical choice changed for many women identified with a BRCA mutation, with the majority electing for bilateral mastectomy.