Defoe was seen wiping away tears after scoring with a spectacular 20-yard volley during first-half stoppage-time in Sunday's Tyne-Wear Derby at Sunderland's Stadium of Light.
The brilliant strike ultimately secured a 1-0 win for the home side, and Defoe divulged that he had been touched by the enormity of derby day in the north east of England.
"I tried to hold it back but it's just a special moment and for the fans as well," the 32-year-old told Sunderland's online channel SAFSee.
"I said before in the presser, coming to the game on the bus and just seeing the kids in the street and how much it means to the people here, it just caught me really.
"The atmosphere was unbelievable, electric, from the warm-up and to score a goal like that and give them something special, it was amazing."
Defoe rated the goal, a left-footed volley after a knockdown from Steven Fletcher, as one of the best of his career.
It was Defoe's third in the Premier League since joining Sunderland in the January transfer window.
"It's definitely up there. I think the strike, how it came about, just before half-time - and it's on my weaker foot, and in a massive game - the game of the season, so I suppose to score a goal like that and get the three points, it's an unbelievable feeling," he said.
"Days like this, this is why you play football. It's just an amazing day."
The victory against their arch rivals lifted Sunderland up to 15th in the Premier League, three points clear of the relegation zone - and ended an eight-game winless run.
"I think the key factor was the energy," Defoe said.
"Everybody worked hard, gave it everything."
