Stroke is a leading cause of death and disability worldwide. The advent of acute reperfusion therapy, intravenous thrombolysis and endovascular thrombectomy, has revolutionized the field of stroke medicine, and neurology in general. Recent studies have implicated a major role of cerebral collaterals in the trajectory of acute ischemic stroke patients receiving reperfusion therapy. Collaterals sustain blood supply to the tissue in the setting of acute ischemia which prevents further expansion of the hypo perfused tissue, playing an important role in determining outcomes after acute ischemic stroke. The use of collateral assessment in routine practice in acute ischemic stroke, let alone in reperfusion therapy, is far from universal and limited. Future work in embedding collateral assessment in standards of care in acute stroke and management is warranted. This article provides a comprehensive update on the diagnostic and prognostic utility of collaterals in acute ischemic stroke and recommendations on collateral-based decision making in acute stroke and steps that can be taken for its rapid uptake in clinical practice.