The monarch kicked off his stay in Poland by opening a business forum at the Polish History Museum in Warsaw.
Later in the day, Frederick X met with Poland's President Andrzej Duda for talks at the presidential palace in the Polish capital.
In the early afternoon, Frederick X laid a wreath at the Tomb of the Unknown Soldier in central Warsaw. He then headed to the houses of parliament for meetings with Poland's lower-house Speaker Szymon Hołownia and upper-house Speaker Małgorzata Kidawa-Błońska.
Later on Wednesday, the Danish monarch attended a signing ceremony for a bilateral agreement on energy efficiency and participated in a round-table discussion focusing on climate-friendly agriculture.
In the evening, the king hosted a gala dinner in honour of the Polish president at Warsaw's Royal Castle, public broadcaster Polish Radio’s IAR news agency reported.
On Thursday, Frederick X is expected to hold a series of meetings with local officials and business executives in Warsaw. In the afternoon, he will fly to Szczecin in Poland's northwest.
On Friday, the Danish king will tour a wind turbine factory in the northwestern Polish city near the German border and attend the signing of a cooperation agreement between the Polish seaport of Szczecin-Świnoujście and Denmark's Esbjerg.
He will also meet with a host of local and regional leaders and visit NATO's Multinational Corps Northeast in Szczecin.
The Danish monarch is being accompanied to Poland by business executives and officials including the country's Foreign Minister Lars Løkke Rasmussen.
On Wednesday, Poland's top diplomat Radosław Sikorski met with Rasmussen for talks in Warsaw on aid to Ukraine.
The Danish embassy in Warsaw has said that the main areas of interest for the business mission led by Frederick X include energy efficiency, climate-friendly agricultural production and biogas.
Frederick X became king of Denmark on January 14, following the abdication of his mother, Margaret II, who reigned for more than five decades.
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Source: IAR, PAP, polen.um.dk