Ospreys won after they snuffed out a spirited second-half comeback by the Italians.
The Welsh region were indebted to a tries from Eli Walker, Hanno Dirksen (2) and Ashley Beck, while 18 points came from the boot of outside-half Dan Biggar.
Treviso scored two tries through Manoa Vosawai and Luke McLean, while Kris Burton supplied seven points with the boot.
Ospreys' Pool Two victory was some revenge for their 12-6 defeat at the hands of the Italian side in the opening game of the RaboDirect PRO12.
Treviso suffered a setback when Alessandro Zanni, their 66-cap Italy openside, pulled out just before kick-off with a back injury.
There had earlier been better news for Ospreys with Justin Tipuric reporting fit despite suffering a hip injury.
Ospreys made a positive start with Biggar kicking three penalties in the opening 15 minutes. He put over his first attempt in the fourth minute after the home side had attacked from the opening two line-outs.
The lead was extended to 6-0 four minutes later when Biggar was successful with a long-range effort after Treviso had transgressed at a scrum as their front eight struggled.
Treviso did get a foothold in the Ospreys 22 but it was immediately snuffed out by some aggressive counter-rucking by the Welsh region, and at the other end the Italians' indiscipline accounted for another penalty which Biggar kicked to extend the lead to 9-0.
Treviso got on the scoreboard with a penalty for Burton on 18 minutes but almost immediately Walker sent the home fans wild with a fine try after weaving his past four would-be tacklers. Biggar converted to give the Ospreys a 16-3 lead.
After a dust-up between the packs referee Neil Paterson sent Wales prop Adam Jones and Treviso captain Antonio Pavenello to the sin-bin.
And Treviso found themselves down to 13 men for two minutes when Vosawai also got yellow-carded after a line-out infringement.
But Ospreys coach Steve Tandy will not have been happy with his side's lapses of concentration at the end of the half which forced them to defend for their lives to preserve their 13-point interval lead.
After regrouping at half-time the Ospreys hit Treviso with a second try four minutes after the break with Dirksen going over in the right corner taking a pass out of the back door from Richard Fussell. Biggar converted as the Ospreys lead was extended to 20.
But Ospreys were then left stunned by two Treviso tries in the space of as many minutes. First Vosawai was on the end of a drive from a line-out before McLean sprinted in unopposed. Burton converted both to cut the home lead to six points.
Biggar stopped the rot on 64 minutes when he put the Ospreys back two scores ahead with his fourth penalty goal.
After hammering at the door for 10 minutes Ospreys scored a third try when Dirksen went over for his second after collecting a chip from scrum-half Kahn Fotuali'i.
And four seconds from the end of time Beck went over for the all-important bonus-point try to end a tricky match on a high note for the region.
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