The three Belarusians, Ales Bialatski, Eduard Lobau and Mykola Statkevich, were jailed after mass protests in Minsk in December 2010 against the re-election of President Alexander Lukashenko.
They were backed for the prize, to be announced October 10 and officially November 20, by some 40 EU centre-right and conservative lawmakers.
Malala, who has become emblematic of the fight against the most radical forms of Islamism, was backed by the three main political groups in parliament, making her a favourite for the award.
Last year's award went to detained Iranians, lawyer Nasrin Sotoudeh and film-maker Jafar Panahi, to honour those "standing up for a better Iran."
Past winners of the 50,000-euro (USD 65,000) prize include South African anti-apartheid hero Nelson Mandela and former UN secretary general Kofi Annan.