The Socceroos star netted in the 24th minute to get the Kiezkicker's promotion charge up and running, but it was a far from straightforward opening outing for the hosts.
Irvine superbly glanced Leart Paqarada's dead-ball delivery home for his goal, and Paqarada netted from the penalty spot to put daylight between the sides.
St Pauli appeared to be out of sight in this encounter when Lukas Daschner's shot found its way in off the upright.
But when the visitors pulled one back at the start of the second half via Kwadwo Duah, it was game on. Enrico Valentini then slammed in a second for the visitors at the death, but it would be too late for Nurnberg to stage a comeback good enough to earn a point, as St Pauli claimed all three.
Kaiserslautern opened the season in Germany's second tier with a 2-1 win over Hannover on Saturday (AEST), and Sunday (AEST) saw wins also for Sandhausen, which beat Arminia Bielefeld 2-1, and Jahn Regensberg, which claimed a 2-0 victory over Darmstadt.
Fortuna Dusseldorf got the job done against Magdeburg, winning 2-1 in the late kick-off, but Greuther Furth had to settle for a point against Holstein Kiel, conceding a late penalty that allowed the visitors to draw level at 2-2, which was the final score.