It was announced on Friday night in Cuba that he had died. He was aged 90.
The Sinn Fein leader gave an address at the weekend at the “international wall” in the lower Falls area of west Belfast (which is home to many murals celebrating republicanism’s overseas links), close to an image of Bobby Sands.
In a statement Mr Adams said he was “extending his condolence with Fidel Castro’s family and the Cuban people following the death of Fidel Castro”.
Flanked by a Cuban flag and Irish flag, Mr Adams addressed the crowd first in Irish, then in English.
He said he had personally met Castro a number of times in 2001, including a six-hour meeting with him.
He described him as “very affable, very [open and] good humoured”, adding that his revolution to overthrow right-wing US-backed dictator Fulgencio Batista in the late 1950s had “led the people of Cuba to freedom”.
He said that there were “criticisms of the system in Cuba”.
“We raised some of those with him about the rights of political prisoners, human rights, and so on,” said Mr Adams.
However, he added that “all societies have their faults and their flaws”, and that prior to his revolution Cuba had been a “two-tier society” with “mass illiteracy” and “mass poverty”.
“All of that was reversed [by Castro]” he said.
“Arguably, they didn’t get it all right,” he said.
“But they got a lot of it right.”
He told those gathered there that Castro had praised the “patriots” of the Irish hunger strikes, adding that the dictator said they had “earned the respect and admiration of the world” for their “moving gesture of sacrifice”.
Castro had added that “tyrants tremble before men who are capable of dying for their ideals”, according to Mr Adams.
He added that Castro “sends a Christmas card every year”, but that “we won’t have one this year”.
A minute’s silence was then observed by those present.
The oration came the same weekend Sinn Fein announced that some of its representatives had met senior members of Hamas.
MLA Declan Kearney, said in a statement on Sunday following the meeting in Istanbul, Turkey, that party representatives “outlined our experience of the Irish peace process and gave an analysis of the current political situation in Ireland”, and that Sinn Fein wants to see “a peaceful, democratic, political agreement” in the region.