Growing up in Sydney he started his medical degree in 1998 at the University of New South Wales graduating with honours in 2003 (BSc Med MBBS Hons). He was an intern and resident medical officer at Westmead Hospital and did his surgical training in Sydney, obtaining his Fellowship with the Royal Australasian College of Surgeons (FRACS) in 2011. This was followed by further subspecialty training in surgical oncology in breast and thyroid surgery. 

Most of his work now involves a mixture of breast surgery (including advanced oncoplastic and reconstructive breast surgery), thyroid and parathyroid surgery, skin cancer surgery and general surgery including laparoscopic hernia and gallbladder surgery. He has a strong presence at the Sydney Adventist hospital and the Northern Surgical Oncology (NSO) San Clinic where he has been working since 2013. He is a breast surgeon at the local BreastScreen Northern Sydney program.

A/Prof. Nicholas Ngui is a prominent breast surgeon at the San where over the years he has made significant contributions and advancements to the breast unit and breast cancer research at the Sydney Adventist Hospital. He is heavily committed to research, with numerous past and current research presented and published in international conferences and peer reviewed journals. He has a strong work ethic and duty of care for his patients. He is a dedicated teacher and supervisor of medical students and junior doctors both in the hospital setting and with the College of Surgeons. At the San he is actively involved with quality improvement through research and chairing the surgery department audit. His practice is current and evidence based. 

A highly regarded surgeon by his fellow colleagues and local community GPs in Northern Sydney and North Western Sydney, all urgent patients are attended to as a priority.