Palace stunned Manchester City on Saturday 1-0, with Ebere Eze hitting the winner. Palace keeper Dean Henderson also denied Omar Marmoush from the penalty spot on the day.
Shearer wrote for BBC Sport: "First Newcastle, now Crystal Palace. As I said on BBC One after Saturday's FA Cup final, 2025 is the year of the underdog - and I love it!
"I know exactly how the Palace fans felt after seeing their side beat Manchester City, because I was there myself only a few weeks ago when Newcastle won the Carabao Cup final.
"Like them, I had waited my entire life to see my team win a major trophy. For Palace supporters this is their first piece of silverware in their history and, from where I was doing my co-commentary at Wembley, I could tell how much it meant to them."
Palace fans played key role
"They reminded me of the Newcastle fans with the way they roared their team on from the moment they got into the ground. For most of the game they drowned the City supporters out, and I went through every emotion with them during the 90 minutes, and especially beyond.
"You could see the agony on their faces when the board went up to show there would be 10 minutes of stoppage time, and when I looked around I saw everyone with their head in their hands - the same way I was when I was waiting for the final whistle in the same stadium against Liverpool.
"I saw the joy and the tears afterwards too, when the celebrations were just getting started. A lot of them will have sore heads on Sunday and Monday, and I don't blame them one bit.
"They knew they had a part to play if their team was going to beat City, and they did it - it was a great performance by Palace's players, but their fans were sensational too."