This was his second win in Bastad following his success in 2023 and the 18th title of his career. It was his first in 17 months since his victory on the hard court in Doha in February 2025.
Rublev, who was top seed, also secured his first title on clay since the Madrid Masters 1000 in April 2024, having previously won the Monte Carlo event in 2023.
Italian Darderi, ranked 18th in the world and seeded number two, showed signs of frustration early in the final.
He was broken on his last service game of the first set and his first in the second, never managing to fight his way back.