Ko has served as mayor of Taipei since 2014 and Chairman of the Taiwan People's Party since 2019.
Before becoming the mayor, he was a doctor at the National Taiwan University Hospital.
He was also a professor at National Taiwan University College of Medicine and specializes in trauma, intensive care, organ transplant, extracorporeal membrane oxygenation (ECMO), and artificial organs among others.
Due to his profession, he has been nicknamed Ko P or KP (which stands for Professor Ko, and is how he is customarily referred to within National Taiwan University).
Ko was responsible for standardising organ transplant procedures in Taiwan, and was the first physician to bring ECMO to Taiwan.
Apart from his practice, Ko is known for his numerous media appearances and interviews as a social and political commentator.
In 2014 Taipei Mayoral Election, Ko ran as an independent candidate.
He beat Democratic Progressive Party (DPP) candidate Pasuya Yao in the unofficial primary, gaining support from the DPP and Taiwan Solidarity Union (TSU).
Ko won the election with 853,983 votes to become the first physician mayor of the city since the introduction of direct election of the office.