Even though Joyce has faced criticism from some ministers, he said that his company "would be active out there, campaigning".
"I believe we have to get behind it and make sure that we have a 'yes' vote and certainly I will be out there strongly campaigning for a 'yes' vote," Joyce was quoted in the media as saying.
Same-sex marriage is illegal in Australia thus far, but it could soon change, according to reports.
A recent survey has concluded that majority of the people are going to vote in favour of the motion in next month's postal plebiscite on whether to legalise gay marriage.
Another prominent voice supporting the movement is Australian Olympian Ian Thorpe.
The swimmer and his partner Ryan Channing have released a video urging fans in support gay marriage.
Same sex marriages were legal for a very brief time in Australia around 2013.
However, a High Court ruling that very year made it impossible for LGBTQ couples to marry legally in the country.
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