Sports Alpha Capital (SAC) will take a 70% shareholding in Northampton Town Ventures Limited, the company which owns the majority of shares in the League Two club.
Existing owners David Bower, Nigel Le Quesne and Kelvin Thomas will collectively retain a 30% stake.
The deal leaves Northampton debt-free following the club's pre-tax loss of just under £3m announced in April 2026.
The takeover also brings an end to Thomas' spell as chairman after more than a decade in the role. He will remain a shareholder and director alongside Bower and Le Quesne.
Thomas was one of the figures behind the takeover of Northampton in 2015 when the club faced a winding-up petition.
Reflecting on his time in charge, Thomas said it had been "an enormous privilege" to lead the Cobblers.
SAC's Joao Xavier and Tim Chamberlain will become the club's co-chairmen, while Pato will join the board as a director.
Chief executive officer James Whiting and supporters' representative Tom Cliffe will also remain on the board. Jim Rosenthal and Mike Wailing will step down as directors and become associate directors.
Xavier and Chamberlain said the new ownership had ambitious plans while stressing the importance of maintaining the club's connection with its community.
"We are extremely proud to become custodians of a club with such a rich history, passionate supporter base and important place within its community," they said.
"We have ambitious plans for Northampton Town, but ambition must go hand in hand with sustainability and an understanding of what the club means to the people of Northampton and Northamptonshire."
The pair said SAC would work with the Community Trust, supporters, staff, partners and local stakeholders as it develops its plans.
"We want the club to continue to be a source of pride within its community and will work closely with the Community Trust, supporters, staff, partners and local stakeholders to ensure that relationship continues to grow."
They added that they expected to spend more time in Northampton and listen to supporters as the new ownership begins its tenure.
"This is the beginning of a long-term commitment from Sports Alpha Capital to Northampton Town Football Club, and we are incredibly excited about the journey ahead."
Further details of SAC's plans are expected to follow.
Pato was named by SAC as one of its investors alongside Gemcorp Capital, a London-based independent investment management firm.
The former Brazil international and his fellow investors attended Northampton's 1-0 victory over Newport County on 5 September.
Pato retired from playing last year and is best known for his five-and-a-half years with AC Milan, where he scored 63 goals in 150 appearances and won the Serie A title in 2010-11.
SAC had previously held discussions over a potential takeover of Colchester United before withdrawing from the process.
Northampton were relegated to League Two last season after finishing bottom of League One. They appointed Chris Hogg as manager in May and brought in 13 players during the summer transfer window, including Manchester City striker Matty Warhurst.
The Cobblers are currently 22nd in League Two, two points clear of the bottom of the table.