The all-stock deal values the merged company at USD 130 billion (118.5 billion euros) and the new group will be split into three separate entities: agriculture, specialty chemicals and materials, they said.
Following the merger, DuPont said it would cut staff by 10 per cent.
Dow Chief Executive Andrew Liveris will become executive chairman of the new company, DowDuPont, while DuPont's CEO Ed Breen will be his CEO.
"This transaction is a game-changer for our industry and reflects the culmination of a vision we have had for more than a decade to bring together these two powerful innovation and material science leaders," Liveris said in a statement.