The royal mingled with guests outside one of the conference rooms, chatting and posing for photographs, before people were let into the room for dinner.
Guests sipped on sparkling wine, but Ms Phillips did the rounds without a drink in her hand.
TVNZ's Toni Street and her former Breakfast co-host Rawdon Christie MCeed the event which celebrated the charity's 10th anniversary.
Richie McCaw, Toni Street, Lance O'Sullivan, Sir Mark Todd, Sir Brian Lochore, Sarah Walker, Aaron Slight and Dion Nash are also patrons of the trust.
Ms Phillips arrived in New Zealand on Thursday and yesterday visited the University of Auckland's Centre for Brain Research.
The 34-year-old is a champion equestrienne and won a silver medal at the 2012 London Olympics as a member of the Great Britain eventing team.