The home side grabbed the lead a minute into the second half after Cesar Azpilicueta gave up possession under pressure from the Brazilian forward, who harried the Chelsea captain into a mistake before slotting a low shot past goalkeeper Edouard Mendy.
After scoring, Richarlison raced down the corner flag and threw a lit blue flare at fans in a dramatic celebration for Toffees. His manager Lampard who is a legend of the visitors was also seen celebrating the goal.
It remains to be seen if he would be punished for this act.
Chelsea dominated possession and Everton had to hold on grimly for the final half-hour. They stay in the relegation zone but move to within two points of Burnley and Leeds United with a game in hand.
Chelsea remain third with 66 points from 34 games as they bid to qualify for the Champions League. They are six points ahead of fifth-placed Arsenal but have now played a game more.