"The co-leaders are the most visible face of the Greens and need to appeal to a wide range of people.
"We need co-leaders that can win those people over, who can overcome the fears of the 28 per cent of voters who considered voting Green in 2014 but did not."
Mr Shaw entered Parliament after the last election and previously indicated it was too soon to contest the leadership.
But this morning at a press conference on Wellington's Cuba Mall Mr Shaw confirmed a change of heart.
The 41-year-old previously worked overseas as a management consultant with firms including PricewaterhouseCoopers, where he helped start the company's sustainable business unit.
He will face off against front-runner Kevin Hague, Gareth Hughes and Vernon Tava for the position that will be vacated by Russel Norman in May.
Mr Shaw said he had grown the Greens' vote in Wellington Central from 21 per cent to almost 30 per cent.
Referencing his relative lack of political experience, he said Mr Norman became co-leader before entering Parliament, and the Greens' other co-leader, Metiria Turei, was experienced and effective.
Mr Shaw said he joined the Greens as a 20-year-old. He has previously formed the London branch of the party, helping to secure a significant expat vote in 2008.
"Achieving a bigger, stronger and more effective Green Party is not about years in Parliament and yelling contests in the debating chamber.
"The Greens need new energy and thinking if we are to grow as a party," Mr Shaw said. "I am the right person, at the right time, to do this job."
