Act is to campaign "globally", sending senior MPs to London, Australia and Hong Kong before the election.
"We believe that our overseas vote is our secret weapon," Act leader Richard Prebble said.
While only 11,482 overseas votes counted in the 1999 election, a law change since had opened up what Act sawas a glorious opportunity.
Voters no longer have to fulfil a legal requirement to make a complete enrolment every three years.
Those living overseas can now download ballot papers from the internet.
They can vote by posting or faxing a ballot paper to the Chief Electoral Office by 7pm on polling day.
Mr Prebble predicted a 10-fold increase in the overseas vote for the July 27 election.
He said an estimated 600,000 New Zealanders lived overseas, of which about 250,000 were potential voters, 174,255 having left the country since the last election.
"Most are young, educated and skilled - the profile of an Act voter. Best of all, most are eligible to vote.
"In the last election Act received 12.8 per cent of the overseas vote.
"As a percentage of Act's total vote, the overseas vote for Act was more than twice as high as any other party.
"An increase in the overseas vote will benefit Act more than any other party."
Act was mounting an email campaign to raise awareness of the election and the need to vote.
Most young people now had an email address, Mr Prebble said.
Its website provides advice on how to download a ballot paper, and vote.
"We are using all of our resources to contact overseas voters. We have been planning this for some time."
Mr Prebble would travel to Hong Kong, where many Chinese New Zealanders lived "temporarily".
Deputy leader Ken Shirley would go to London, where 60,000 young New Zealanders were thought to live.
Justice spokesman Stephen Franks would travel to Australia.
All three trips would be funded out of the MPs' own pockets, Mr Prebble said.
Act would send other MPs to Australia during the campaign "should we deem it necessary".
