Triple-negative breast cancer (TNBC) is the most aggressive and deadly subtype of breast cancer, accounting for 30,000 cases annually in the US. While there are several clinical trials ongoing to identify new agents to treat TNBC, the majority of TNBC patients are treated with anthracycline- or taxane-based chemotherapies in the neoadjuvant setting, followed by surgical resection and adjuvant chemotherapy. While many patients respond well to this approach, as many as 25% will suffer local or metastatic recurrence within five years. Understanding the mechanisms that drive recurrence after chemotherapy treatment is critical to improving survival for patients with TNBC. It is well-established that the extracellular matrix, which provides structure and support to tissues, is a major driver of tumor growth, local invasion and dissemination of cancer cells to distant metastatic sites. In the present study, we show that decellularized extracellular matrix (dECM) obtained from chemotherapy-treated mice increases motility of treatment-naïve breast cancer cells compared to vehicle-treated dECM. Tandem-mass-tag proteomics revealed that anthracycline- and taxane-based chemotherapies induce drug-specific changes in tumor ECM composition. The basement membrane protein collagen IV was significantly upregulated in the ECM of chemotherapy-treated mice and patients treated with neoadjuvant chemotherapy. Collagen IV drove invasion via activation of Src and focal adhesion kinase signaling downstream of integrin α1 and α2, and inhibition of collagen IV-driven signaling decreased motility in chemotherapy-treated dECM. These studies provide a novel mechanism by which chemotherapy may induce metastasis via its effects on ECM composition.