Thousands of mines were planted in the Gulf Arab state during a two-month civil war in 1994 that was triggered by an attempt by leaders of the former South Yemen to form a new separate state.
Landmines killed dozens of people since they were planted.
"Aden has now become free of landmines. This great catastrophe has been lifted," said Yemeni Prime Minister Abd al-Qadir Bagammal.
About 30,000 landmines have been removed and more than 170,000 landmines, grenades and explosives detonated in the area, a Yemeni official said.
Bagammal said a programme initiated in 1999 and sponsored by the United Nations and other countries to eradicate thousands of mines in the rest of the country would go on until the whole country was purged of the deadly landmines.
Yemen was among many countries that signed a treaty in 1997 to ban anti-personnel landmines.