The Polish No.8 seed was beaten by unseeded Spaniard after a three-set match 6-3, 3-6, 3-6, and failed to capture his sixth career singles title.
In the first two sets, both players showed great serving consistency, as each of them was faced with only one break. The third set, however, was a display of Carreño Busta's stunning conversion rate, who eventually managed to come back from a set down to a 2-1 victory in the tournament's final.
Earlier on Sunday, Hurkacz partnered by Poland’s Jan Zieliński was handed a loss by Britain's Daniel Evans and Australia's John Peers in the doubles semifinal, 5-7, 6-4, 4-10.
In June, the Polish 25-year-old claimed his fifth ATP singles title by defeating world No. 1 Daniil Medvedev in the final of Germany’s Halle Open grass-court tournament.