Ulster exploited Filo Paulo's second-half sin-binning as they held off improving Treviso in the Pro12 game at the Stadio Comunale di Monigo.
Luke Marshall's early try helped Ulster lead 7-0 but Treviso bossed most of the first period as two Tommaso Allan kicks cut the margin to 10-6 by half-time.
However captain Rob Herring and Ruan Pienaar scored Ulster tries during Paulo's absence in the third quarter.
After Herring's sin-binning, Tommaso Benvenuti notched a late Treviso try.
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