Last year, the 65-year-old he confirmed he's be leaving TVNZ at the end of 2018.
He began working at TVNZ in 1979 as a rugby league commentator after starting out at Radio Otago in 1972.
Most recently he had been weekend newsreader and fill-in for Simon Dallow on the weekday 6pm news.
Originally a sports journalist, Williams has fronted some of New Zealand's biggest news events, including seven Olympic Games and the Pike River disaster in 2010.
He was also the host of Mastermind and a Breakfast presenter.
He is now a columnist at the Bay of Plenty Times.
He had been commuting to Mount Maunganui since 2010 when his wife, Sarah Lunam, took up a job at the Port of Tauranga.