Ngawini began his career in rugby union, having been contracted to the Waikato ChiefsSuper 12 franchise for four years beginning 2001. In 2001 he was also selected in the All Black 7s training squad with the likes of Joe Rokocoko and Eric Rush. Ngawini switched to rugby league in 2004, attracting national media attention in a standout performance for the NZ A side that beat the Kangaroo XIII in a 2005 Test. Ngawini featured in Ngati NRL documentary on Maori TV, which follows a number of Maori boys trying to crack the Australian NRL competition.
Bulldogs career
Debut: Vs Parramatta – 14 May 2006 Dog Years: 2006, 2007 Ngawini joined the Canterbury Bulldogs in 2006 as a, but was developed into playing at. He received the opportunity to play in the NRL in Round 10 against the Parramatta Eels. He went on to play a further two games in the top grade against the Cronulla-Sutherland Sharks the following week and then in Round 14 against the Canberra Raiders.
Ngawini left the Gold Coast Titans at the end of the 2008 NRL season to move back to rugby union, and began the transition by joining the Gold Coast Breakers squad in the Queensland Premier Rugby. Debut: Vs Souths – 4 April 2009 He made an exciting start to the 2009 season for the Breakers, playing at fullback and first-five. His excellent footwork, fast pace, accurate passing and deft offloads assisted in many scoring plays. Helped the Breakers climb to second in the competition table after eleven rounds. Despite only playing the first half of the season, Ngawini had the third highest number of votes in the Alec Evans Medal for the best and fairest player in the Queensland Premier Rugby. During his time playing rugby union on the Gold Coast, he was also selected to play for the Queensland Reds 2nd XV.
After three hugely successful years with Rugby Club I Cavalieri Prato including a well publicised performance against Stade Francais in the Amlin Challenge Cup, Ngawini moved to Rugby Rovigo Delta as part of an extensive recruitment drive by the club. He quickly became a crowd favourite at Rugby Rovigo Delta, scoring 15 tries in his first season alone, winning the accolade of most tries scored in Italy in the 2013/14 season.
Wicklow RFC
For the 2017/2018 season he joined Irish Junior rugby team Wicklow Town RFC, playing in Leinster Division 1A, deploying his step alongside such greats as Dean H Leonard and Tommy O Donovan. Playing at scrum half and winger Billy scored many tries and received many many yellow cards.