O'Donovan scored again in first-half injury time when he deflected in a cross at point-blank range from Dimi Petratos, who had run around Paracki almost to the byline. It was the former Central Coast frontman's seventh goal of the season.
Andrew Nabbout gave Newcastle a stranglehold on the game on 54 minutes after O'Donovan's back heel and Joey Champness' pass put him into space. Nabbout cut back on to his right foot and buried his shot.
The result leaves Wellington without a win this season and lifts Newcastle to 11 points from five matches.
Phoenix skipper Andrew Durante provided a succinct summation after the match: "We were our worst enemy [last night]. We gave the ball away in silly areas and got what we deserved."
One of the few positives for the Phoenix was the return of Durante, who can now come into consideration for the All Whites side to face Peru on Saturday.
"It's nice to be back and good to get through 90 minutes when I was supposed to be out until mid-January," said Durante.
Newcastle 3 (R. O'Donovan 37, 45+1, A. Nabbout 54)
Wellington 0
Halftime: 2-0