The defender played the full 90 minutes at Atlanta Stadium, in what was his major tournament debut for La Roja and his 19th total international cap.
Star man Lamine Yamal opened the scoring 10 minutes in for the European champions, who were held to a draw by Cape Verde in their opening match, which was also in Atlanta on Monday (15 June).
Mikel Oyarzabal soon extended their lead, poking in from close range after 21 minutes before popping up at the far post for his second just three minutes later.
Pedro had an involvement in the Real Sociedad forward’s second strike, finding Marc Cucurella in the opposition’s penalty area, who picked out Dani Olmo before he sent a header across goal, which was pounced on by Oyarzabal.
Spain got their fourth four minutes into the second half, with a corner being bundled in by Saudi defender Hassan Al Tambakti in the aftermath of a save from a Marc Cucurella strike by goalkeeper Mohammed Al Owais.
Our number 23 had the chance to further extend their lead five minutes later after being put through on goal by fellow defender Pau Cubarsi, but Pedro’s low strike was well saved by Al Owais.
The three points put Luis de la Fuente’s side at the top of Group H before the game between Cape Verde and Uruguay tonight (11pm BST on BBC One), which wraps up the second round of fixtures for the group.
An important final game for Pedro and his teammates then follows against Uruguay, and Rodrigo Bentancur, as they look to win a World Cup group for just the second time since being crowned champions in 2010.
Pedro and Lolo will face off in the early hours of next Saturday morning (27 June, 1am BST) at Guadalajara Stadium in Mexico.