Metastatic melanoma has long been considered to have a very poor prognosis and to be chemo-resistant. However, a subgroup of patients with metastatic melanoma presents remarkable responses to chemotherapeutic agents, even in the absence of a response to modern targeted therapies and immunotherapies; accordingly, determining predictive biomarkers of the response to chemotherapies for metastatic melanoma remains a priority to guide treatment in these patients. We report a case study of a patient with B-Raf proto-oncogene serine/threonine kinase-mutated metastatic melanoma harbouring many genetic mutations. The patient did not respond to prior targeted therapies or immunotherapies but experienced a dramatic objective radiological and clinical response to subsequent dacarbazine-based chemotherapy. In the era of targeted therapies and immunotherapies for metastatic melanoma, cytotoxic chemotherapies may still represent an interesting therapeutic weapon in a well-defined subgroup of patients presenting with specific genetic and molecular features.