On 18 August 2014, Fiorentina confirmed that they had reached an agreement for the season-long loan of Marin from Chelsea with an option to buy. On 23 October, Marin made his début for Fiorentina in a Europa League match against PAOK. Marin scored his first goal for the Italian side on 27 November 2014, in a Europa League match against Guingamp. In the sixth minute, Marin was able to pick up Aquilani's pass and clipped home the opening goal, as Fiorentina edges out the French side in a 2–1 win. On 11 December 2014, Marin scored in a 2–1 loss against Dinamo Minsk.