Horowhenua-Kapiti Rugby Union chief executive Corey Kennett said the union's players were already looking forward to what would be a memorable occasion.
"To play at Westpac Stadium will be a special occasion for the players, management, and the whole rugby community. It's certainly something that they will cherish for a long time.
"I see a lot of common ground for the three provinces, and we actively work together where possible to assist each other. I am also extremely grateful for the support of PGG Wrightson, who have offices in all three unions, and who have come on board to sponsor the match for the next two years."
Wairarapa-Bush Rugby Union chief executive Tony Hargood said the match was an illustration of the close relationship between the three unions involved.
"The Wairarapa-Bush union is looking forward to what is always a highly competitive and enjoyable rivalry with Horowhenua Kapiti, but also to recognising our close relationship with the Wellington Rugby Football Union.
"This match represents a real opportunity to put the Heartland Championship out there in the public eye and we have no doubt it will generate plenty of interest from the rugby communities in all three unions."
With the curtainraiser to kick off at 3:05pm and the Lions match at 5:35pm, it promises to be a family friendly afternoon.
It won't be the first time Horowhenua Kapiti and Wairarapa Bush have played each other at Westpac Stadium with the two provinces contesting a non-competition match in 2012 as a curtainraiser to a Hurricanes' Super Rugby match.
Westpac Stadium double header, Saturday, September 3:
Mitre 10 Heartland Championship
Horowhenua-Kapiti v Wairarapa Bush
Kickoff 3:05pm
Mitre 10 Cup
Wellington Lions v North Harbour
Kickoff: 5:35pm