The announcement comes after two state broadcasters began bidding against each other, both funded with taxpayer money.
Prime Minister John Key and Maori Affairs Minister Pita Sharples brokered the joint bid, and the independent bids by MTS and TVNZ were withdrawn.
Mr Key and Dr Sharples announced the Government's support for the joint bid at a press conference, both saying it was the best way to ensure free-to-air access to all matches and at the same time showcase Maori culture.
Mr Key said the joint bid would receive government money, but he was not going to say how much until it was known whether the bid was successful.
He said it would go to the International Rugby Board "fairly immediately" and a response was hoped for later this week or next week.
There has been speculation the joint bid is costing about $5 million, shared between the three networks.
Mr Key said there would be money for the state broadcasters from the Government's coffers, while TV3 would pay its own way.
MTS would receive extra funding from Te Puni Kokiri (the Ministry for Maori Development) to purchase "related services" if the bid was successful, Mr Key said.
Under the new, Cabinet-approved joint bid MTS would broadcast all 48 World Cup games -- 16 live and 32 delayed.
The final, semifinals, bronze medal game and the quarterfinals will be live on all three channels.
TVNZ and MTS will screen live the opening ceremony and opening game between Tonga and the All Blacks.
The All Blacks' pool game against France will screen live on TV3 and MTS.
Mr Key said he was pleased all three broadcasters had worked "so collaboratively" to finalise the bid and they were all happy with the agreement.
The joint-bid, which still has to be accepted by the IRB, would mean all New Zealanders would get to see the games, he said.
Dr Sharples said he was "delighted" MTS would be leading the joint-bid and the three broadcasters would work together for the first time for "the benefit of the whole country".
A governance group would be established to oversee the project.
MTS board member Wayne Walden will chair the group. Members from each of the broadcasting companies and two ministerial appointments will form the remainder.
Television Broadcasters' Council executive director Rick Friesen will be the lead manager for the project.
Maori commentator Derek Fox said MTS could still feel "aggrieved" because they put together an innovative bid for exclusive free-to-air coverage of the Rugby World Cup.
"I understand MTS is saying they're happy and maybe that's what they have to say.
"MTS did nothing wrong -- they talked to people, they put together a credible bid and then they've had that whipped away by prejudice," Mr Fox told NZPA.
TVNZ and TV3 who did not put together a credible bid would now benefit anyway, he said.
MTS not only has to share the games but must share the "important" one.
It was "unfair" and "shows prejudice does work", Mr Fox said.
Labour Broadcasting spokesman Brendon Burns said the Government's coordination of the joint bid was a "face-saving formula" which came about after a shambles.
It should have happened weeks ago but the Government stood by and let a vacuum develop which MTS tried to fill, he told NZPA.
