Scarlets held off a determined Treviso fight back to claim a RaboDirect PRO12 bonus-point win as they moved up to sixth in the overall standings.
The Welsh outfit were 15 points up at one point early in the second period before the hosts closed the gap to a point as they trailed 33-34 with five minutes left.
However, Jordan Williams' late score for the visitors sealed a 41-33 victory.
A try double by Frazier Climo and further touchdowns from Gareth Davies, Kristian Philips and a penatly try had put Simon Easterby's team in control, a position enhanced by 11 points from the boot of fly-half Aled Thomas.
But Robert Barbieri, Meyer Swanepoel and Ludovico Nitoglia pushed Treviso back into match with tries of their own. Home full-back Matt Berquist added 18 points as the Italians looked set to push Scarlets all the way in the closing stages.
But just as they looked set to tip the game in their favour, Williams found his way to the line before Thomas converted to ensure victory for the Welsh side.