Newcastle battled to a nervy 29-27 win at Petrarca in their Amlin Challenge Cup Pool Five opener.
The Falcons trailed 17-10 at the break and 27-24 with a little more than a quarter-of-an-hour remaining before a late Micky Young try sealed a bonus-point victory.
Ed Williamson, Danny Williams and Lawrence Ovens all joined Young in crossing the Petrarca line, but the overall performance was far from convincing.
Newcastle made nine personnel changes and a positional switch from the side that lost to Saracens last weekend, and that decision nearly backfired on director of rugby Steve Bates.
Driving rain before kick-off made conditions difficult, but Bates will have been disappointed with the ease with which the Italian minnows claimed three tries of their own.
Former Gloucester fly-half Ludovic Mercier controlled proceedings for the hosts until he limped off injured just past the hour-mark.
Although Newcastle conceded their third try shortly after Mercier's departure, Petrarca looked a far weaker side without the 32-year-old's commanding presence at the Stadio Plebiscito.
Defeat looked like a distinct possibility when they conceded a penalty 35 metres out with less than two minutes to play. But Stefano Ambrosio slipped on contact, and the Flacons survived.