Jamie Vardy scored a second-half penalty double as Leicester condemned West Brom to a disappointing return to the Premier League.
After goalkeeper Sam Johnstone twice came to the home side's rescue with saves to deny Harvey Barnes in the first half, new signing Timothy Castagne broke the deadlock when he nodded home a far-post cross from fellow Belgian Dennis Praet nine minutes after the restart.
Vardy, last season's Premier League top scorer, then got up to score from the spot after being dragged back by Kyle Bartley as he chased into the box to support a move that saw Johnstone deny former Baggies loanee Barnes for a third time.