Petkov, who made a handful of appearances for Bulgaria between 1998 and 2018, came on for Nikolay Krustev (26) in stoppage time to set the record at the age of 47.
The veteran even saved a penalty, celebrating with his team mates with a shushing gesture, but the VAR asked for it to be retaken as he was not on his line and Georgi Valchev scored the winner in the 98th minute when he was given a second chance.
"Petkov is a very experienced and cunning goalkeeper. I'm glad that even on the second time, I managed to outsmart him," Valchev was quoted as saying by Top Sport.
"It's no coincidence that he has been in football for so many years. A big 'bravo'!"
In August 2018, Petkov had set the previous record for the oldest player in the Bulgarian top flight, marking that occasion with a man-of-the-match performance in a 0-0 draw with champions Ludogorets.