The Engineering, Printing and Manufacturing union, or EPMU, says its members have voted overwhelmingly in favour of a merger with the Service and Food Workers Union.
After voting closed at 5pm yesterday, it said 84 percent had voted in favour, and nearly 96 percent of the SFWU's members had voted in favour.
The EPMU's national secretary Bill Newson said it was an historic occasion for both unions.
He said by joining forces they could build their strength and capability to stand tall for the workers of New Zealand.
The new union will be formally launched, with a new name and brand, in October.