Davey Hall, Amicus northern regional secretary, predicted severe disruption after employees in the purchasing department voted 17 to five in favour of stoppages over plans to relocate them 240 miles away to Cranfield, Bedfordshire.
Mr Hall accused Nissan of treating workers as if they were "robots" and complained that the firm had refused to discuss the proposed relocation with the union.
Amicus claims to represent 30% of the site's 4,500-strong workforce and the strike threat is the first at a Japanese company since the leftwing Amicus leader, Derek Simpson, vowed to take a tougher line with companies.
Nissan was attracted to the north-east with grants in 1984, and this is the Washington factory's first strike ballot.
Nissan said employees agreeing to move to its Cranfield site would receive relocation allowances of up to £7,500 plus six years' help with higher mortgages.
"Our discussions so far have been reasonable and amicable and we are hopeful that the matter can be quickly resolved," a Nissan statement said.
The Washington factory is rated the world's most efficient car plant and is on target to produce 350,000 Micras, Primeras and Almeras this year, including some models exported to Japan.
