Residents of the Caribbean island nation waved flags, held posters with photographs of Castro and laid down flowers at his tomb in the Santa Ifigenia cemetery.
"We are the legacy, we are what Fidel wanted for the revolutionary youth. We will never betray the commitment we have for the revolution of Fidel and his leaders," said state worker Michael Pena.
Among them was Castro's grandson Fidel Antonio Castro Smirnov.
Fidel Castro died on November 25, 2016 at the age of 90.
He ruled for 49 years, outlasting nine U.S. presidents in power and building a communist state on the doorstep of the United States that defied all Washington's efforts to topple him.