The party won victories in Baghdad and Basra and appeared to be the largest group in mainly Shia provinces in southern Iraq.
With about 90 percent of the votes counted, candidates backed by al-Maliki who formed the country's State of Law Coalition secured 38 percent of the vote in Baghdad with the nearest rival getting 9 percent, according to the Iraqi High Electoral Commission, reported the Agence France-Presse.
In Basra, Maliki's allies garnered 37 percent with the runners-up settling in around 12 percent, according to the AFP.
In Mosul in northern Iraq, a Sunni faction had a strong showing after boycotting the last nationwide elections in 2005.
The parties backed by anti-U.S. Shiite cleric Muqtada al-Sadr also fared well. But the Islamic Supreme Council of Iraq, led by cleric Abdul Aziz al-Hakim, lost ground even in Hakim's home base of Najaf. And the Shiite Islamist Fadhila party, which had held the governorship in Basra, all but disappeared, according to The New York Times.
In Karbala, Maliki's home province, a secular civic leader narrowly edged out the Dawa candidate, the Times reported.
More than 14,000 candidates from 400 political parties and lists participated in the Jan. 31 elections in 14 of Iraq's 18 provinces. Kirkuk and three northern Kurdish provinces did not take part in this election.
Just over half of Iraqis voted in the election, which was considered the next major step in the country's democratic process.