The six were connected to the Danish activist group Fighters and Lovers, which sold shirts printed with Farc and PFLP logos.
Thursday's verdict overturned a lower court ruling last December acquitting all seven after finding that the two organisations were "not really terrorist" groups.
The appeals court disagreed, ruling that the Farc and the PFLP are "terrorist organisations that have committed acts aimed at destabilising a state or a government and have attacked civilian targets".
The court ordered the confiscation of the approximately $4,850 the company had made on the sales.
Both the Farc and PFLP are classified as terrorist organisations by the United States and the European Union.
Two of the defendants were sentenced to six months in prison, while four others were sentenced to shorter, suspended prison terms, the Eastern high court in Copenhagen said in a statement.
A seventh defendant was acquitted.
The maximum prison sentence for the charges under Danish law is ten years.
Thorkild Hoeyer, the group's lawyer, said that they would appeal against the verdict to Denmark's highest court.
'Legitimate' movements
During the trial, Fighters and Lovers said the Farc and the PFLP were legitimate liberation movements and likened their support of the groups to supporting the African National Congress in South Africa in the 1980s.
According to legislation adopted in Denmark following the September 11, 2001 attacks in the United States, any direct or indirect financing of "terrorist" organisations is punishable by up to ten years in prison.
The verdict last December had marked the first time that a Danish court had ruled on how to consider Danish citizens' support for groups that figure on the EU designated terrorist group list.
The defendants said on Thursday that they had been expecting a new acquittal and were surprised and disappointed by the verdict.
"The Danish judicial system reveals today that it stands on the side of the occupying power Israel and of a Colombia that kills its people and tortures prisoners," Michael Schoelardt, the head of Fighters and Lovers, said.
"We must continue our fight for peace and justice in the world and develop our solidarity work... despite this (Danish judicial) system that wants to criminalise it."
Hoeyer said he he was willing to take the case all the way to the European Court of Human Rights.