The spotlight was on new £49 million man Raheem Sterling, but it was David Silva and Yaya Toure who stole the show to help ease City to three points.
Toure was influential in City’s first two goals, first producing a shot which was flicked by Silva and then deflected off defender Craig Dawson on its way in, and the second a fine finish before the 25-minute mark. Vincent Kompany then completed a comfortable triumph for the visitors just before the hour.
City, and their old guard, were too strong for the Baggies, for whom Saido Berahino wasted their best chance.
Sterling should have also marked his debut with a goal, but was denied by Boaz Myhill when clean through. The 20-year-old started in support of Wilfried Bony, with Sergio Aguero on the bench, while Albion handed debuts to Rickie Lambert, James Chester and James McClean.
Albion’s new £12m record buy Salomon Rondon was unveiled to the crowd hours after signing from Zenit St Petersburg, along with Arsenal loanee Serge Gnabry.
But the new boys would have watched in horror as City dismantled their hosts in the first half. City took the lead after nine minutes with a goal which happened almost in slow motion. Silva’s cross-shot found the waiting Jesus Navas at the far post and he teed up Toure on the edge of the box. The midfielder was gifted time to shoot and his mishit effort was flicked on by Silva before hitting the helpless Dawson and crawling across the line.
The visitors underlined their dominance in ruthless fashion after 24 minutes. This time there was no doubt over the scorer as Toure swapped passes with Bony before unleashing an unstoppable effort into the top corner from 20 yards.
The hosts emerged for the second period with renewed belief. First, Lambert’s 30-yard free-kick whistled over before Berahino’s tame finish fell to the under-worked Hart.
The striker should have done better and was left to rue the miss when City made it 3-0 on 59 minutes as Kompany glanced in Silva’s corner with his shoulder.
West Brom: Myhill, Chester, Dawson, Lescott, Brunt, Gardner, Fletcher, Morrison, McClean (Yacob 46), Lambert (Anichebe 74), Berahino (McManaman 80). Subs not used: Olsson, Ideye, Sessegnon, Rose.
Man City: Hart, Sagna, Kompany, Mangala, Kolarov, Toure (Demichelis 80), Fernandinho, Jesus Navas, Silva, Sterling (Nasri 74), Bony (Aguero 63). Subs not used: Zabaleta, Caballero, Denayer, Iheanacho.