Gylfi Sigurdsson converted from the spot to punish a rash Edouard Mendy challenge as Everton toppled Chelsea on Merseyside.
Ancelotti endured a miserable return to Stamford Bridge last season with his current employers, Everton going down 4-0 in the capital.
However, he came out on top in a second meeting with Frank Lampard, who was part of the Chelsea squad who secured a domestic double under the Italian coach in the 2009-10 season.
The only goal of the game arrived in the 22nd minute thanks to an early Christmas gift from Edouard Mendy, the goalkeeper needlessly charging into Dominic Calvert-Lewin as the striker attempted to get on the end of his own flick-on from Jordan Pickford’s long punt.
Sigurdsson calmly rolled in his attempt from the spot for his first league goal in 17 games, much to the delight of the 2,000-strong crowd inside Goodison Park.
Chelsea responded brightly to the setback of falling behind, Reece James striking a post with a low drive that Pickford appeared to get a slight touch to, while Kurt Zouma – who spent a season on loan at Everton earlier in his career – planted a close-range attempt straight at the England goalkeeper.
Richarlison failed to capitalise on a clear shooting opportunity before the break for the hosts, slipping as he struck the ball with his left foot to make Mendy’s life easier.
Sigurdsson went close with a free-kick early in the second half and was then denied the chance to take another penalty when a VAR check found Calvert-Lewin offside prior to being bundled over by Ben Chilwell.
Still, one goal proved enough as Chelsea failed to find an equaliser, despite Lampard sending on Tammy Abraham in place of the ineffective Kai Havertz to partner Olivier Giroud up top.
Mason Mount saw a free-kick kept out by a post as Everton held firm, in the process securing a third successive home win over their opponents as they moved into the top half.
FT. Big performance. Big win.
UP THE TOFFEES!!!
— Everton (@Everton) December 12, 2020
What does it mean? Sweet success for depleted Toffees
Everton had stuttered after an excellent start to the 2020-21 season, winning just once in their previous seven league outings after opening up with four wins on the spin.
Their cause was not helped by a shortage of full-backs – Mason Holgate and Ben Godfrey did an admirable job either side of the excellent Michael Keane and Yerry Mina – in what was a battling display, as shown by them having just 28 per cent possession. Indeed, Chelsea failed to manage an on-target attempt in the entire second half.
Sigurdsson pulls the strings
Everton’s captain created six chances for his team-mates before making way in the closing minutes, while no one else on the pitch created more than two.
In it for keeps?
Mendy had seemingly solved the keeper conundrum at Chelsea, conceding just twice in seven league games prior to the trip to Merseyside. However, Lampard will have every reason to question why the signing from Rennes felt the need to rush out and confront Calvert-Lewin when the situation was under control.
Chelsea are back on the road again during a full round of midweek Premier League fixtures, travelling to Wolves on Tuesday. Everton have an extra day to recover before they visit Leicester City.