The opposition boycott was expected to give Abdoulaye Wade's ruling Sopi coalition a walkover win in the polls, allowing it to extend its control over a recently enlarged 150-seat National Assembly.
Full results were not expected before Monday.
Opposition leaders had urged citizens to stay at home to contest what they said was octogenarian Wade's increasingly autocratic style and his refusal to discuss alleged flaws in the presidential poll that re-elected him in February.
|Wade casts his vote on Sunday in Dakar [AFP]|
"The turnout was clearly lower than in the presidential elections," said the head of one polling station in Dakar's Point E district.
Turnout in February was 70.5 per cent.
The opposition hailed their boycott strategy as a success.
"This is a real slap in the face for Wade," said Dialo Diop of the Siggil Senegal (Stand up Senegal) opposition coalition, which had distributed leaflets urging voters to snub the polls to "save democracy" and "fight Wade's monarchy".
The boycott and voter apathy risked tarnishing Senegal's image as a model of democracy in Africa.
The mainly Muslim country has won a reputation for political, religious and ethnic tolerance since independence from France in 1960 and has suffered no coups, a unique record in turbulent West Africa.
Some voters said they had lost faith in the ballot box.
Many fear the opposition boycott will remove any effective check to Wade, who has already been criticised for harassing political foes and media critics with temporary detentions.
He was enthusiastically elected in 2000, ending four decades of Socialist rule, but since then has faced criticism for not doing enough to end poverty, unemployment and high prices.