Made with Kashmir as its backdrop, the film was honoured at the fest, which concluded Saturday.
The crime drama's stars Shahid Kapoor and Shraddha Kapoor are overjoyed.
"1st festival 1st win. Too much. Wowzaaaa. People's choice in the main category at the Rome film festival... A first for an Indian film. #haider. Proud and humbled," Shahid tweeted Sunday.
Shraddha, who gave another hit "Ek Villain" this year, is thrilled too by the honour to "Haider".
"We WON! #Haider - the 1st Indian film to win the main category of people's choice award at Rome film festival! So humbled, grateful & proud!," she tweeted.
"Haider" hit the screens Oct 2 and got rave reviews by critics worldwide. Since the word-of-mouth was strong in India, the Rs.22 crore-film did good business too.