The passengers were on their way to Ausaneshwar Ghat of Gomati river in Barabanki district for the immersion of Durga idol yesterday when the mishap took place, police added.
The tractor-trolley overturned near Chilauli on Lucknow- Varanasi National Highway 56 under police outpost Inhauna, police said.
While Ajay Singh (26) died on the spot, Gangadin Passi (80) died on his way to trauma centre in Lucknow.
Three persons are still being treated in hospital, police said.
Meanwhile, a 14-year-old girl Shivani was runover by a tractor near Sarvajit market in Barabanki district, SHO Shivratanganj Dinesh Yadav said.