Salah, who joined Fiorentina last week on loan from Chelsea, made his Serie A debut in Sunday’s 3-2 home triumph over Atalanta.
The 22-year-old came on as a second-half substitute against Atalanta and Montella was impressed with his performance.
“Salah is an unpredictable and talented player,” Montella told his club’s official website. “He will improve even more.”
Fiorentina hold an option to extend Salah’s stay for a further 12 months at the end of the season.
Salah made just three Barclays Premier League appearances for Chelsea after joining the Blues from Basle in January 2014.
Montella is confident the Egypt international will have a starring role following the departure of Colombia winger Juan Cuadrado to Chelsea last week.
Unlike attacking duo Alberto Gilardino and Alessandro Diamanti, who also joined Fiorentina during the winter transfer market, Salah was included in Fiorentina’s squad list for the Europa League.
“It’s obvious that Salah still needs to have a period to adapt,” Montella said. “But I think he will be very useful.”
Fiorentina are fourth in Serie A, seven points adrift of Napoli, who are third and hold the last Champions League qualifying spot.
The Viola face Tottenham in the Europa League Round of 32 later this month.