Pierre-Emerick Aubameyang has now scored 33 goals in his first 50 Premier League games, as many as Fernando Torres managed.
The Magpies rarely threatened once Aubameyang lashed home after Ainsley Maitland-Niles’ fine work on 58 minutes.
Newcastle earlier saw Jonjo Shelvey hit a post and new £40million forward Joelinton head wide.
Arsenal starting with many of their £125m-worth of signings on the bench and without midfielders Mesut Ozil and Sead Kolasinac, Gunners boss Unai Emery watched his side struggle to cut through their opponents in the first half.
That all changed just before the hour mark when Aubameyang was left unmarked on the edge of the area, collected Ainsley Maitland-Niles’ cross from the right and fired past Martin Dubravka.