"I am announcing to you that I have made the decision to run for president again," the country's leader told his supporters at a rally in the center of Prague marking the fourth anniversary of Zeman's inauguration.
On Friday, a press conference will be held at the president's residence, where Zeman will officially announce his decision.
According to the 72-year-old president, he had a thorough medical check-up before making his decision to run for office and was found fully fit, except for a problem with his leg.
Last week, a poll by the Czech Public Opinion Research Centre (CVVM) showed that 54 percent of the respondents had confidence in Zeman, whose approval rating had remained stable over the last few months.
In 2013, Zeman triumphed over then Foreign Minister Karel Schwarzenberg with 54.8 percent of the votes in the first direct election of the president. Zeman ran as the candidate from the Party of Civic Rights, which he founded in 2009.
