Newcastle emphatically halted a run of four Premier League games without victory as Eddie Howe’s team inflicted a first defeat on new Leicester manager Ruud van Nistelrooy.
The Magpies dominated the first half and took the lead when Jacob Murphy, who had already spurned two good opportunities to put the home side ahead, fired low into the corner following a clever corner routine.
Alexander Isak shot too close to Mads Hermansen in a one-on-one with the Leicester goalkeeper, but the home side remained on the front foot in the second half and were 3-0 up within five minutes of the restart.
Bruno Guimaraes headed in from close range following another well-worked set-piece, before Isak nodded home from a similar position after Lewis Hall’s cross was deflected into his path by Conor Coady.
Murphy fired over the crossbar not long afterwards and Isak sidefooted straight at Danny Ward – a half-time substitute for Hermansen – but the Magpies’ winger eventually made it 4-0 with a low drive past the substitute keeper.
The hosts could have rubbed further salt into Leicester’s wounds late on as Sandro Tonali fired into the side-netting and former Foxes forward Harvey Barnes curled a left-footed shot wide of the far post.
Victory lifted Newcastle up to 11th, while Leicester remain precariously placed in 16th spot, two points above the bottom three.