Sitting President Jose Eduardo dos Santos, in power since 1979, is expected to win another five-year term.
Unita, a former rebel group during the country's 27-year civil war and now the main opposition party, has called for a delay to the election, charging irregularities. The BBC reports polls in Luanda opened on time despite fears of logistical problems.
International monitors said the elections appear to be fair but opposition members disagree.
Marcolino Moco, a former member of Santos' government who had a falling out, told The Guardian newspaper: "The way he is ruling the country, it is not possible to have normal elections because he controls everything: communications, oil, money, people.
"It is worse than the elections in 2008 and even 1992. Today Dos Santos is openly doing these things. The observers are saying everything is OK but my God, everything is not OK."
Controlled by Portugal until 1975, oil-rich Angola has seen an economic boom since resolving its long civil war, the BBC said. Government opposition, though, says the money derived from the nation's oil drilling has only benefited the society's elites.
Santos' party, Popular Movement for the Liberation of Angola, is expected to win about 80 percent of the Parliament's seats. Unita has campaigned on a growing unrest with Santos and the MPLA party.
The BBC notes nearly half the nation's citizens don't have regular access to electricity or clean water.