The acquisition will be completed after the deal receives regulatory approval, the two companies said at the Dubai Airshow.
Following completion of the deal, Darwin will rebrand as Etihad Regional and realign to connect passengers from secondary European cities with Etihad's main network, they said.
Darwin Airline serves secondary European markets from its Geneva hub, flying 10 50-seat Saab 2000 turboprop aircraft.
Etihad holds equity investments in several airlines, including 29 per cent in airberlin, 40 per cent in Air Seychelles, 19.9 per cent in Virgin Australia and three per cent in Air Lingus.
