The information minister said the move was to mourn the revolutionary leader, who died on Friday at the age of 90.
Cuba was one of the first countries to establish diplomatic relations with The Gambia after Mr Jammeh took power in a coup in 1994.
Mr Jammeh, 51, is seeking re-election for a fifth term in office.
For the first time since he came to power he will be facing a single major opposition candidate.
Earlier this month, Human Rights Watch accused him of using violence to silence critics ahead of the 1 December poll and said two activists had died in custody and dozens of people had been jailed and denied medical or legal help.
Mr Jammeh had strong links with Castro, with the Cuban leader sending doctors to work in The Gambia.
Gambia's President Yahya Jammeh has suspended his campaign for Thursday's election as a mark of respect for Cuba's Fidel Castro.