Museveni who has been in power since 1986 won a sixth term in office fighting off a challenge by former singer Bobi Wine.
According to the country's election commission, Bobi Wine, whose real name is Robert Kyagulanyi came second in the polls.
The EC said Museveni received 58% of the vote to 34% for Wine.
But Wine rejected the results and alleged that votes were rigged, as election officials face questions over how results were tallied amid an internet blackout.
Ahead of the vote, Museveni's government shut down social media outlets in Uganda, from Facebook and Instagram to Twitter. It also sent military vehicles into the streets.
He said "We are the real winners of this election and therefore what the electoral commission announced has nothing to do with the real election that took place.
"I can call on all Ugandans to reject the announcement that has been made by the electoral commission...to reject them with the contempt with which it deserves."