Jamie Vardy’s second-half strike for Leicester handed Everton their fourth defeat in five games in an error-strewn Premier League encounter at Goodison Park.
The England forward’s 58th-minute goal was one of the few highlights of a turgid affair.
Full-back Ricardo Pereira capitalised on defender Michael Keane’s error to play in the England striker, who finished with an angled drive past Jordan Pickford.
Everton were not much of a force in attack, with Jonjoe Kenny’s first-half shot off the bar the closest they came to scoring.
The Toffees, who have now not won in their past four home games, remain 10th in the table, while Leicester move above Wolves into seventh place.
Defeat caps miserable Christmas for Everton
Everton spent more than £200m on players in two summer transfer windows, but some fans will be wondering where their quality signings have been hiding in recent games.
A 5-1 win at Burnley has been the only highlight of a rotten festive period in which they have conceded 12 goals in five games and failed to score in their past two.
Foxes keeper Kasper Schmeichel was tested only twice in the game, by substitute Cenk Tosun on both occasions. The first was a firm 20-yard strike which he punched clear before the Dane reacted to push away a close-range header late on.
It was a mistake by £30m signing Michael Keane, who failed to control a Leicester long ball, which resulted in the decisive goal.
He and the rest of the Everton players will hope to avoid another slip-up when they host League Two side Lincoln City in the FA Cup third round on Saturday.
Vardy class proves the difference
In contrast to Everton boss Marco Silva, Leicester counterpart Claude Puel has had a wonderful festive period.
That is now three wins in four games, with those victories coming against Chelsea, Manchester City and Everton.
Those were the type of sides the Foxes were beating during their title-winning season in 2015-16.
They lack the consistency of that campaign and have lost some key players since, but one standout act from that season has remained and he once again made the difference.
Vardy only had one shot on target in the match, but he made it count. It was one of his typical finishes, running on to a through-ball before striking home left-footed from an angle.
The celebration was less typical – a cartwheel and a somersault.
Poor advert for the Premier League
The first 15 minutes of a forgettable first half were farcical. Two teams, laden with millions of pounds of talent, could barely hold on to possession for more than a few seconds.
The graphic below illustrates the misplaced passes during that period. Everton’s Kenny was the worst culprit of the 20 outfield players – he attempted 14 passes, with an accuracy of only 35.7%.
Leicester defender Ben Chilwell lost possession 22 times in the first 45 minutes, having only done so on 17 occasions in the entire match against Cardiff three days ago.
Everton are at home to Lincoln City in the third round of the FA Cup on Saturday (15:00 GMT), while Leicester travel to Newport County on Sunday (16:30).