- Arthur Cabral (25')
- Andy Diouf (71')
- Zeki Amdouni (90'+2')
The Swiss Super League side are now in a solid position to become the first team from their country to reach a European final.
Basel thought they had taken an early lead but the effort was ruled out for offside following a VAR check.
Arthur Cabral headed Fiorentina into the lead after 25 minutes with his seventh goal of this season's competition but he did not celebrate out of respect for his former club Basel where he played from 2019-2022.
Fiorentina dominated the possession but Basel slowly established a foothold in the game and became more threatening as it wore on.
Andy Diouf equalised after 71 minutes with a well-placed low shot from just outside the box and Amdouni silenced the Italian fans three minutes into added time when he fired home from 10 yards after a free kick was floated towards the back post.
The return leg will be played next Thursday in Basel.
- Francois Letexier