The Employment Court has ruled Carter Holt Harvey was not entitled to make its workers take annual leave during the Covid-19 lockdown in April 2020.
There were around 260 staff at the Marsden Point timber manufacturer when the lockdown was announced.
Members of E tū union took the company to court after it required employees to use eight days' annual leave during the third and fourth week of the nationwide lockdown.
The court found the company made no attempt to reach agreement with its staff over taking the leave and it wasn't entitled to require workers to take their holidays.
The Council of Trade Unions said the decision could have widespread implications for other workplaces.