Biopsy of suspected metastases in patients with breast cancer is recommended in the practice guidelines of the National Comprehensive Cancer Network, but not always performed in routine oncology practice, often because of the cost and invasiveness of the procedure. Biopsies can confirm the presence of metastatic disease, reveal unsuspected benign disease or second (non-breast) malignancies and confirm expression of biomarkers, all of which can aid the optimal management of the cancer. Image-guided biopsy has increased the accuracy and safety of the procedure. Here, we aim to provide a practical algorithm for deciding when to perform biopsy of suspected breast cancer metastases, in order to optimize clinical practice. We expect that future clinical trials and standard-of-care practice will increasingly obtain tissue from metastases to assess molecular differences (DNA, RNA, protein) between the primary tumour and metastases. Advances in targeted therapy for breast cancer will be highly dependent on the availability of metastatic tissue. In this article, we provide an up-to-date review of the current issues in biopsy of suspected metastases in patients with breast cancer, including technical details of biopsy, pathology review of biopsy specimens, and interpretation of biopsy findings.