The European Commission has approved a tie-up between Fiat and Chrysler, saying the move would not hurt competition in Europe.
Chrysler and Fiat completed an agreement last month to form a new auto company after the Italian group stepped in to salvage the bankrupt US firm.
The move completed a quick restructuring of Chrysler in a plan backed financially by the US and Canadian governments.
Fiat will at first hold 20% of Chrysler Group, rising to 35% and eventually to a majority stake.
Fiat will help Chrysler develop more fuel-efficient vehicles and will use Chrysler's sales network in exchange.