Neither candidate has ever held political office but they beat out two prime ministers and the candidate for the moderate religious party Ennahdha.
Tunisia's electoral commission on Tuesday said law professor Kais Saied and detained media mogul Nabil Karoui won the most votes in Sunday's presidential election, beating major political leaders to advance to a second-round runoff.
The commission's announcement following a full count of votes confirmed exit polls released on Sunday evening and partial results issued throughout Monday.
Sunday's vote has been seen in Tunisia as a sharp rebuke of the established political forces that have dominated since the 2011 revolution, failing to address economic troubles that include high unemployment and inflation.
Saied took 18.4 percent of the votes and Karoui took 15.6 percent. Of the other 24 candidates, who included the prime minister, two former prime ministers, a former president and the defence minister, the Ennahda candidate Abdelfattah Mourou came in third with 12.9 percent.
Saied, little known before the election, is a constitutional law professor who ran a modest campaign with next to no publicity or funding, espousing conservative social views while pushing for a return to the principles of the 2011 uprising.
Karoui, a well-known but controversial figure, is the owner of a major TV news channel and the founder of a large charity that focuses on the plight of Tunisia's poor.
He was detained weeks before the election over a tax evasion and money laundering case brought three years ago by an independent transparency watchdog.
He denies all wrongdoing and his supporters attribute his arrest to political manipulation. He was unable to take part in televised debates before the vote and electoral monitors have voiced concern that voters have been deprived of a chance to hear him campaign.