He is 56 and was the first to set up an Innovation Bureau for his city. The mayor embraces innovative technology. He even has a Twitter account with half a million followers - and counting. He calls it his "Twitter administration".
"I use Twitter to communicate [with citizens] because it can reach out to a lot of people. I have been encouraging other government officers to do the same," says the former human rights lawyer who became Seoul's mayor last October.
In the 1970s, when he was a university student, he was jailed for four months for demonstrating against the former authoritarian president Park Chung-hee.
Park Won-soon surprised many when he won the mayoral race. He had no former experience in the job. But he promised to take care of the poor and needy.
Recently, he twittered to tell his followers that he was in Hong Kong for the launch of the Social Innovation Exchange (Six) Asia. "I told them I'm doing something good in Hong Kong," he says with a smile.
Six is a global network of individuals and organisations that promote social innovation around the world. Six Asia was launched in partnership with Jockey Club Makes a Difference (MaD) School, a platform for those who want to be change makers through the sharing of ideas and taking action with global partners.
In Hong Kong, Park explained the importance of listening to people.
"Some citizens complained about the lack of lights on the street, I listened and [the government] handled the problem," he says.
"Their problems may sound trivial but not to me. Small is important. If you let them build up, they will become big problems. If I deal with something when it's small, I won't be faced with a big problem later on. All government policies should be based on opinions from the people and for the people."
To gather opinions at a grass-roots level, Park appointed three honorary vice-mayors. They are ordinary citizens and represent the young, the handicapped and the elderly.
"They can talk to our government directly. They can also arrange to meet me if they want to discuss any issues raised among their groups," he says.
Park is also a philanthropist who founded the Beautiful Foundation, a local charity, before he became mayor. He stresses he values the benefits of sharing and using innovative solutions to problems.
To promote creativity, he set aside 52.7 billion won (HK$32 million) to support young and new social entrepreneurs. He allocated another 72.5 billion won (HK$48.6 million) to support community services and facilities, including day care centres, gardening and farming enterprises and art spaces.
Park also opens government spaces and resources to the public. He urges corporations to do the same. "I think it's high time we changed from an economy-driven society to a humanistic one."
This month, he was elected as the next chair of the World Mayors Council on Climate Change. He has pledged to make Seoul a greener city. He has created "Cool Biz guidelines for civil servants", which allow them to wear shorts and sandals in the summer to reduce the need for air-conditioning in offices.
To set an example, Park wears sandals to the office. He also modelled at the "Cool Biz Fashion Show" on Environment Day.
"Participation is very important for anything to happen. I want Seoul to be a happy and fun city. We can make our dream come true - if we work together," he insists.