Kawau made his provincial debut for Otago in 2003 but unfortunately due to a major knee injury in the lead up to the first game of the season he only made it back for the final 2 games of the 2003 season. In 2004 he made 6 appearances for Otago. Due to a lack of consistent game time Kawau transferred to Southland in 2005, where his career would blossom.
Kawau spent 5 seasons as a starter in the Stags' backfield, making his 50th appearance during the 2009 Air New Zealand Cup. His tenure with Southland would end on a high with the team's Ranfurly Shield triumph over Canterbury near the end of the 2009 season.
After impressing for Southland, Kawau was called into the Highlanders squad part-way through the 2006 Super 14 season as an injury replacement, and made two appearances. He was a full squad member the following season, and scored 3 tries in just 6 appearances. However, he was not included in the Highlanders squad for 2008.
Kawau returned to Super Rugby in 2009 when he was drafted to the Hurricanes and made 9 appearances, mainly as a substitute. He was back with the Hurricanes in 2010, but missed most of the season due to injury, only returning for 6 matches at the end of the year.
Kawau signed in Japan with the Kobelco Steelers for the 2010–11 season.