Background: Bernard O’Brien significantly advanced microsurgical techniques in Australia. He extended his medical and surgical training with specialised studies in England and New York, focusing on the potential of microscopes in Plastic Surgery. Methods: O’Brien’s research centred on refining microsurgical techniques, particularly in small vessel anastomosis using microscopes. Collaborating with experts like Professor Gerard Crock, he developed advanced micro-instrumentation and micro-sutures, crucial for successful microvascular surgeries. This work laid the groundwork for clinical microsurgery and innovations in lymphatic surgery. Results: Key advancements by O’Brien included a 70 μm needle and 19 μm thread for micro-sutures, enhancing the success rate of anastomosing vessels under 0.5 mm in diameter. His efforts led to major breakthroughs in free tissue transfer, microlymphatic surgery for lymphoedema, and hand and thumb reconstructions. His work was crucial in training over 200 microsurgeons and founding the International Society of Reconstructive Microsurgery. Conclusions: O’Brien’s contributions to Plastic Surgery, especially in microsurgery, were groundbreaking. His innovations in microvascular techniques and equipment significantly propelled the field forward. Through his leadership and education, he influenced new surgical methods and trained a generation of microsurgeons, leaving a lasting impact on the global practice of Plastic Surgery. His legacy is marked by the widespread adoption and enhancement of microsurgical techniques. Ref: O’Brien BMC, Henderson PN, Crock GW. Metallized microsutures. Med. J. Aust. 1970; 1: 717–9.