"The last time I was in here, [Nick] Swisher asked me if I could hit a ball up there," Branyan said. "I told him I didn't know, because it looked a lot further than the old stadium.
"I guess the answer is 'Yeah.'"
The mammoth blast gave the Mariners a two-run lead, but they eventually dropped a 9-5 decision, which took much of the thrill away for Branyan.
"It feels pretty good when you hit a ball like that," he said.
It was his third home run in the past two games in the Yankees' spacious playground and his seventh since the facility opened last season.
None of the others measured up to his prodigious blast off Yankees right-hander Javier Vazquez.
Branyan said he never saw where the ball landed, but others did.
"For him to hit the ball that far is absolutely amazing," Yankees center fielder Curtis Granderson said. "I think I've seen [Mark Teixeira] go close, but Branyan's hit today was further than that. Absolutely amazing.
"There's something about him in this ballpark that he really likes."
The Yankees never announce the distances of opponents' home runs, but the club said it was the first time in the stadium's history that anyone hit a ball that far up into the seats during a game. A fan wearing a Yankees T-shirt snagged the ball.
"A home run is a home run no matter how far it goes," Branyan said. "It doesn't matter if it goes five rows deep or 20 rows deep."
Yankees shortstop Derek Jeter agreed.
"It was pretty good, I guess," he said. "They all count the same."
But this one is sure to be discussed for quite some time.
"I can't get hung up on one home run," Branyan said. "But it definitely felt good. I knew I got it when I hit it."