The midfielder netted his second and third strikes of the season as the Blues came from behind to win 3-1 at Selhurst Park.
Gallagher spent the 2021/22 season on loan at Palace and was a huge hit amongst their fans as he scored eight goals and assisted a further five in all competitions.
However, he didn't hold back in his celebrations for Chelsea on Monday night, with the 24-year-old scoring the winner away at the south London outfit for the second season in a row.
Sky Sports presenter David Jones said after the match that Palace fans thought he loved them but he keeps coming back to score at their expense.
And with a wide grin on his face, Gallagher admitted: "I do love them, that's the thing. It's sad but you can't beat that feeling, so I'm sorry Palace fans."
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His first goal of the game came in the 47th minute and the crucial second was scored in stoppage-time, with the midfielder shouting and running towards the away end on both occasions.
Despite showing his passion for the club he has been at since the age of eight, one talkSPORT caller questioned the level of his celebrations.
Calling into the Sports Bar, Shaun said: "When Gallagher scored, I just didn't like his celebration, it was too early in the game. If you score last minute... if he scored his second goal first, I'd get it, 90th minute, you've got the winner, you run into the crowd.
"But it was like the 60th minute and I thought to myself, 'Palace fans loved him when he was there for the season.' And I was thinking about how much it means to the Palace fans not seeing a player celebrate."
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Jermaine, a Palace fan, also said: "[Malo] Gusto was running rampant all game long and he's caught us on the break and Gallagher has come in and scored his first goal, it's a shame that he's had to celebrate really because he was well loved by the Palace fans."
Gallagher has now scored three goals in his last two Chelsea appearances having previously gone 34 matches without netting.
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The Blues fell behind on the night during a poor first-half showing as Jefferson Lerma curled in an excellent strike from range for Palace.
Roy Hodgson's side were caught napping in the early stages of the second-half though, with Gallagher firing in a half-volley from Gusto's cross.
He then struck low into the bottom corner at the beginning of stoppage-time to complete the comeback, with Enzo Fernandez also netting moments later to seal all three points for Chelsea.