The new boys were rarely troubled by an Iraq side that defended in numbers, but showed little threat in their opponent's half.
Inter Milan striker Lautaro Martinez, playing only his second game for the national side, put Argentina ahead after 15 minutes with a superb header from a Marcos Acuna cross.
Roberto Pereyra doubled their lead eight minutes into the second half when he took a pass on the edge of the box and swept a right-foot shot home after the Iraq defence opened up in front of him.
Defender Pezzella grabbed a third eight minutes from fulltime when he headed home after a flick on at a corner and Franco Cervi added a fourth in injury time after a surging run from midfield.
"It wasn't easy opening them up but we managed it and we were patient and managed to score more goals," Pezzella said.
The win took Argentina's unbeaten run under interim coach Lionel Scaloni to three games.
Since taking over from Jorge Sampaoli after Argentina's poor performance at the World Cup in Russia, the South Americans have beaten Guatemala and Iraq and drawn with Colombia, without conceding a goal.
Argentina's next game is on Tuesday against arch rivals Brazil in Jeddah.
(Reporting by Andrew Downie; Editing by Toby Davis)
