In 2002, he gave $7.5 million to the University of Auckland Business School and has also supported the Millennium sporting institute and Hockey New Zealand.
Last year's grand finalists open the new NRL season against the Manly Sea Eagles at Eden Park on Sunday.
"Like Eric, I see the NRL as the best sporting product there is in this part of the world and I'm thrilled to now be part of it," Glenn said.
"As New Zealanders we are known for achieving above our station and the Vodafone Warriors are no exception having made the finals in four of the past six years. I've been incredibly impressed with the management of the club in recent years and I'm extremely positive about its future.
"Both Eric and I have very similar thinking when it comes to how important a role sport plays in the lives of young people.
"Not only does it ensure young people are kept busy but it is a catalyst for encouraging confidence, determination, focus and healthy bodies and minds, while fostering team work - all of which are vital elements needed to contribute to society. This has been a motivating and driving factor in my investment in the Vodafone Warriors.
"I don't profess to be an expert when it comes to the game of league, and I will certainly be leaving that side of things to Brian (McClennan), but I'm a strong advocate for the benefits sport plays in young people's lives."
Watson, who bought a 75 percent stake in club in 2000, said his new joint venture partner would bring not only his business acumen to their venture but also a similar passion for the club, for the NRL and for the wider benefits rugby league can bring to people's lives.
"When Newcastle and St George Illawarra kicked off the NRL season last night, it proved yet again why the NRL competition is by far the best sporting product throughout Australasia," said Watson.
"The Vodafone Warriors are the biggest single sporting franchise in the country but we don't want to stop here. We want the Vodafone Warriors to become the most successful club in the NRL."
- NZ Herald Online staff