Pellegrini was hired by City's Abu Dhabi-based owners to revitalise a team that surrendered the Premier League title to Manchester United last season and the Chilean's new players responded by delivering a stylish victory in his first match in charge.
With title rivals United and Chelsea both winning under new management over the weekend, it was essential that former Malaga boss Pellegrini kept pace at the top.
City delivered emphatically as Spanish midfielder David Silva headed the opener in the sixth minute and Argentina forward Sergio Aguero steered in the second in the 22nd minute.
Newcastle's troubles continued when defender Steven Taylor was sent off just before half-time for catching Aguero with a forearm.
Yaya Toure's superb 50th minute free-kick made it three and Samir Nasri came off the bench to complete the demolition with a cool finish 15 minutes from full-time.
Newcastle, who have only signed QPR striker Loic Remy on loan since Joe Kinnear was brought in to take care of transfer activity, faced disruption before the match, with France midfielder Yohan Cabaye being left out of the squad following a £12 million bid from Arsenal.
But while Newcastle were abject, City made quite a statement about their intentions for the season
Many predicted that Pellegrini, who replaced Roberto Mancini at the end of last season, would employ a 4-3-3 formation following his move to England, but he stuck with the 4-4-2 he has used throughout pre-season against Newcastle.
An indication of the depth available to Pellegrini is that he had a powerful bench including Alvaro Negredo and Nasri and there was no place in his 18-man squad for Stevan Jovetic, Gareth Barry or Micah Richards.
Fernandinho and Jesus Navas were the only two pre-season additions to start but City wasted little time in showing their ambition for the new campaign.
Edin Dzeko forced a fine early save from Tim Krul after being picked out by a cross from Pablo Zabaleta.
And after just six minutes City moved in front when a forceful run from Dzeko ended with the Bosnian's cross kicking up off Taylor and Silva guided a header into the corner of the net.
Dzeko missed with a low cross-shot soon after but City moved two ahead before the mid-point of the first half.
A Navas pass was flicked on by Dzeko and Aguero burst through, making enough space around Taylor to squeeze a low shot past Krul.
City were able to pull their visitors open at will and Dzeko was unlucky not to get a toe on the end of a Navas free-kick.
Hatem Ben Arfa provided Newcastle's only flicker of creativity and the French winger drove a bending effort wide of goal.
Yet Newcastle's hopes were effectively finished when Taylor was shown a straight red card for catching Aguero with his arm.
Krul did well to keep the deficit at two goals when he swatted away a header from Dzeko after the Bosnian was picked out by a fine cross from Aguero shortly after half-time.
But seconds later City did extend their lead when Ivory Coast midfielder Toure bent a free-kick into the top corner from just outside the area.
Krul pulled off another impressive stop when he pushed a powerful Dzeko effort past the post just after the hour and the striker also turned a header wide from Silva's corner.
Nasri added the fourth when he reacted quicker than Mathieu Debuchy to a Zabaleta pass and guided a shot past Krul.
New striker Negredo came off the bench in the closing stages and after Krul pushed away Dzeko's header, the Spaniard had a first goal for the club wrongly ruled out for offside.