The EU, which Romania joined in 2007, has already put its justice system under special monitoring and was critical last year over attempts by the ruling coalition to impeach President Traian Basescu.
It has been especially keen that prosecutors in one of the bloc's most corrupt states should not be political appointees, but analysts said the appointments had ended up the result of a compromise between Romania's fractious powerbrokers.
Prime Minister Victor Ponta chose the candidates for the prosecutor general's office, the anti-corruption department and the organised crime unit last month without applications or interviews.
The Commission has widely praised previous prosecutors' work, which has led to the conviction of several high level public officials including former prime minister Adrian Nastase.
But critics said some of the new appointees had political connections that would make it difficult for them to pursue the anti-corruption drive.
They have also expressed concerns that Tiberiu Nitu, the new head of Romania's prosecution office, is insufficiently prepared after Basescu initially rejected him late last year.
"I am convinced he can handle the position and that the judiciary will not collapse, nor will it be controlled politically," Basescu said. "Those who believe we could have delayed the appointments further ... are mistaken."
Meanwhile, the choice to appoint Brussels-praised former prosecutor-general Laura Codruta Kovesi to head the anti-corruption unit was criticised by a faction of Ponta's alliance.
At the time Ponta picked the team, an analyst said the nominations appeared to be aimed at easing tensions between and within political parties.
Ponta's coalition is loose alliance of liberals and leftists, who have long been at loggerheads with the rightist president, and the names would have had to have mostly satisfy the demands of all sides.
"The appointments are the result of a political consensus, which was needed for anything to get done," said Sergiu Miscoiu, an analyst with the CESPRI political think tank.
"The changes at the anti-corruption unit are such that could keep up the standards. The general prosecution appointments are the other side of the compromise, where there are ... some legitimate concerns over management abilities."
Under Romanian law, the president appoints chief prosecutors nominated by the justice minister. Ponta was acting as interim justice chief at the time of the nominations.
(Editing by Alison Williams)