Unions estimate 200 striking workers from SkyCity in Auckland joined a rally at lunchtime on Saturday, to push for a higher wage offer.
They're unhappy with the current 4% offer, and want staff who have been with the company a long time to earn more than those who have just joined.
Protesters carrying placards and using loudspeakers paraded around the SkyCity complex.
Striking engineer Rangi Archibold says his whole team walked out in protest at what they say are low wages.
Mr Archibold says it's unfair people that people starting work with the company can earn more than people who have been there many years.
SkyCity disappointed at strike action
SkyCity disputes that a large number of staff are backing rolling industrial action at the Auckland casino.
The company says there were far fewer than 200 people protesting, and most were not employees.
SkyCity's general manager of group services Grainne Troute says the union has been premature in striking.
"We've been in what we thought were productive discussions over what we see as a fair offer in line with inflation and the increased cost of living," she says.
"So we are really surprised and disappointed that the union has decided to instigate a strike."