Selection of women for treatment-focused genetic testing (TFGT) following a new diagnosis of breast cancer is changing. Increasingly a patient's age and tumour characteristics rather than only their family history are driving access to TFGT, but little is known about the impact of receiving carrier-positive results in individuals with no family history of cancer. This study assesses the role of knowledge of a family history of cancer on psychosocial adjustment to TFGT in both women with and without mutation carrier-positive results. In-depth semistructured interviews were conducted with 20 women who had undergone TFGT, and who had been purposively sampled to represent women both family history and carrier status, and subjected to a rigorous qualitative analysis. It was found that mutation carriers without a family history reported difficulties in making surgical decisions quickly, while in carriers with a family history, a decision regarding surgery, electing for bilateral mastectomy (BM), had often already been made before receipt of their result. Long-term adjustment to a mutation-positive result was hindered by a sense of isolation not only by those without a family history but also those with a family history who lacked an affected relative with whom they could identify. Women with a family history who had no mutation identified and who had not elected BM reported a lack of closure following TFGT. These findings indicate support deficits hindering adjustment to positive TFGT results for women with and without a family history, particularly in regard to immediate decision-making about risk-reducing surgery.