Background: The vascular delay phenomenon is a foundational concept in reconstructive surgery, used to improve flap reliability in situations of marginal perfusion or high risk of ischaemia. Despite its long history, delay remains variably understood and inconsistently applied in contemporary practice. Purpose: To review the historical development, physiological basis, and current clinical applications of vascular delay, and to highlight emerging concepts relevant to modern reconstructive surgery. Methodology: A narrative review of the literature was performed examining the historical origins of vascular delay, proposed physiological mechanisms, experimental and clinical evidence, and contemporary indications. Recent advances in flap physiology, imaging, and microsurgical techniques were also reviewed to explore evolving perspectives on delay. Results: Vascular delay induces adaptive changes that improve flap survival, including augmentation of choke vessel calibre, redistribution of blood flow, enhanced venous outflow, and increased ischaemic tolerance. Historically applied to pedicled flaps, delay continues to play a role in selected local, regional, and perforator-based reconstructions. Advances in microsurgery, perforator flap design, and preoperative imaging have reduced routine reliance on delay; however, it remains valuable in compromised vascular territories, reoperative fields, and high-risk patients. Emerging concepts include pharmacological preconditioning, ischaemic conditioning, and imaging-guided patient selection. Conclusion: Vascular delay remains a relevant and adaptable strategy in reconstructive surgery. Understanding its physiological basis and appropriate indications allows surgeons to selectively apply delay to improve outcomes while avoiding unnecessary procedures in the modern era.