It was a case of third time lucky for the 30-year-old playmaker, who was also nominated for the award in 2017 and 2018.
Tuwai was a key figure as Fiji won titles in Cape Town, Hamilton, Hong Kong, London and Paris to secure the 2018/19 World Series title, their first since 2016, and was named in the World Series 'Dream Team' for the third year running.
The Olympic gold medallist is the first Fijian player to win the award since Samisoni Viriviri in 2014.
He said Fiji's sevens success is a group effort.
"I think it's all about the love and passion that we have for the game and the bond that we have for each other."
He's the first Fijian player to win the award since Samisoni Viriviri in 2014.
Meanwhile former Manu Samoa captain Papaliitele Peter Fatialofa was one of six people inducted into the World Rugby Hall of Fame at last night's awards ceremony in Tokyo.
His wife Anne accepted the award on behalf of her late husband, just three days shy of the sixth anniversary of his death.
"I think for everybody, including...my kids, it's an honour and it's such a privilege and it would have been really nice if he was here to accept it," she said.
"So, on behalf of Kerr's Road and everybody else I would like to say thank you World Rugby for this inducting, it means so much to us."
South African flanker Pieter-Steph du Toit and England centre Emily Scarratt were awarded the men's and women's players of the year awards, with Rassie Erasmus taking out the coaching gong and the world champion Springboks recognised as the team of the year.
USA hooker Joe Taufete'e, who was born in American Samoa, was also nominated for the men's award.