The Swedish ambassador to Belarus, Stefan Ericsson, has returned to Minsk after being withdrawn in February along with other EU ambassadors, an embassy spokesman said.
The diplomatic exodus in February was the culmination of strained relations following the arrest of Belarusians protesting the results of presidential elections in December and the EU's subsequent imposition of sanctions on Belarus.
The EU has since expanded the number of blacklisted Belarusian officials who face travel and other restrictions.
The Polish ambassador to Belarus, Leszek Szerepka, has also returned, Polish radio reported. Szerepa is currently in the Belarusian city of Brest.
The Belarusian ambassador to Belgium, who is Minsk's representative at EU institutions, and the head of the Belarusian embassy in Poland, have likewise returned to their duties.