Portugal Telecom shareholders on Thursday overwhelmingly approved the 7.4-billion-euro ($8.4 billion) sale of the operator's Portuguese assets to France's Altice.
The green light removes the last obstacle to the sale of the assets, which have been owned by Brazil's Oi since May as part of its merger with Portugal Telecom.
Portugal Telecom is a minority investor in Oi with the power to block a sale.
"Oi is very pleased with the outcome of the vote," said Oi's chief executive Bayard Gontijo, adding that 97 percent of the shareholders had voted in favour of the sale at a general meeting in Lisbon.
Oi acquired Portugal Telecom's assets last year under a merger deal between the two operators and committed to the sale to Altice in early December.
It is the third major acquisition by Altice -- a growing cable, telecoms and communications giant -- following purchases of French companies SFR and Virgin France.
Portugal Telecom employs about 11,000 people, and controls 40-50 percent of Portugal's cellular and ADSL business.