It is one of Poland's slimmest presidential election victory since the end of communism in 1989, where one of the major issues was the future of the country's strained relations with the European Union.
President Duda is a social conservative allied with the government led by the nationalist Law and Justice (PiS) party, while Trzaskowski is the socially liberal mayor of Warsaw..
Duda's win is expected to lead to further reforms to the judiciary and continued popular opposition to abortion and gay rights..
At a press conference last 13 July, the heads of the electoral commission said they were not sure when complete results would be announced, as some polling stations had yet to submit their counts..
However, with 99 percent of all constituencies reporting, those tallies were not expected to affect the result. Turnout was reportedly 68.2 percent..
The opposition Civic Platform (PO) group - which backed Mr Trzaskowski - told Reuters news agency it was collecting information on voting "irregularities" after the polls closed on Sunday, including reports of Poles abroad not receiving their voting packages in time to take part in the election.