Petrauskas attacked from the off, but incurred a warning for hitting after he had called break.
That gave the Italian two points to his total, but it forced the Lithuanian to attack even more.
Valentino was under constant pressure and found himself trailing by one point after the first round.
The Italian managed to slow the action down more in the second, but still found it hard to shake off Petrauskas, who extended his lead to 12-9.
The Lithuanian connected with a two-punch combination that wobbled Valentino early in the third round. However, the referee then gave Petrauskas another warning.
Despite losing four points through warnings, Petrauskas prevailed 16-14.