The Egypt international's loan move to Roma was not a breach of the contract signed with the Viola, the world football governing body ruled on Wednesday
Egypt international Salah signed for Chelsea from Basel in January 2014 and went on loan to Fiorentina a year later, making 16 Serie A appearances for the club.
The 23-year-old winger was then loaned to Roma last season, prompting Fiorentina, who expected to have the player again in 2015-16, to claim a breach of contract had taken place.
And while the decision of FIFA is not final, it appears Chelsea are set to be cleared of any wrongdoing in the matter.
"We can confirm that the dispute resolution chamber (DRC) dealt with the dispute opposing the Italian club, ACF Fiorentina, to the player, Mohamed Salah Ghaly, and the English club, Chelsea FC," FIFA said in a statement.
"The findings of the relevant decision, without grounds, have been communicated to the parties on June 8, 2016.
"The claim of the Italian club was rejected. Since the decision is not yet final and binding, we are not in a position to comment on it any further."
Salah remains under contract at Stamford Bridge and has been tipped to join Roma on a permanent basis, but could yet be retained by incoming manager Antonio Conte.