"In a state governed by the rule of law decisions of the Constitutional Court must be respected (...) Romania's president signed today the decree" to sack Kovesi, Iohannis' office said in a statement.
The prospect of Kovesi's removal had attracted vehement criticism from the opposition and concern from the international community.
Kovesi had held the high-profile post since 2013 and was considered a symbol of the fight against graft in one of the EU's most corruption-plagued members.
Iohannis, who is from the centre-right and has frequently clashed with the government, had initially said he was "not convinced" by arguments to remove Kovesi, leading prominent figures in the ruling Social Democratic Party (PSD) to raise the prospect of his impeachment.
The DNA had stepped up the campaign against corruption among local and national elected officials in recent years, earning accusations of abuse of power and the enmity of many in Romania's political class.
In February, Kovesi noted that despite "unprecedented attacks" by the government, in 2017 the DNA had brought 1,000 people to trial, including three ministers, five MPs and a senator.
Over the winter, thousands of protestors took to the streets in support of Kovesi and to oppose her sacking.
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