The pair, who already own the NBA's Philadelphia 76ers and the NHL's New Jersey Devils, will join chairman Steve Parish in control at Selhurst Park.
Harris, Blitzer and Parish will each own an 18 per cent stake in Palace.
Parish said shareholders had agreed an "initial £50m injection of capital" to develop the club's stadium.
Parish helped rescue the south London club from bankruptcy in 2010. His partners in that deal - fellow Palace fans Stephen Browett, Jeremy Hosking and Martin Long - will have smaller stakes.
"I'm delighted that Josh and David have agreed to make this investment and join me in shaping the future of Crystal Palace," said Parish.
In a joint statement, Harris and Blitzer said: "We couldn't be more excited to be joining the Crystal Palace family. We were drawn to the club's rich history, exciting brand of football, strong leadership and, above all, its passionate fans.
"We look forward to supporting Steve in his role as the operating co-owner and leader of the club. Crystal Palace has a storied legacy, a bright future and we're proud to become a part of it."
Parish told BBC Sport last month that the planned deal would enable the club to tackle a chronic lack of investment in Palace's facilities over the last 25 years, without "diverting funds from the team".
Most pressing for Parish is the need to redevelop the Main Stand at Selhurst Park, but he also wants to improve the Arthur Wait Stand and the Whitehorse Lane End, as well as upgrade the club's training ground and scouting network. There are long-term plans to build a hotel and shops at Selhurst Park.
The cost of the building work on the ground alone ranges from a reported £50m to £150m.