The pair plays again on Thursday in Kuala Lumpur before meeting in Macau two days later.
The battle between the past and present tennis giants, who met only once in competition -- the Swiss winning a five-set thriller in the fourth round of Wimbledon [ Images ] in 2001 -- provided rousing fare for the crowd at Seoul's Olympic [ Images ] stadium.
If the Swiss star, who won his fourth Masters Cup title Sunday in Shanghai, expected an easier time against the 36-year-old American, who retired in 2002, he was in for a surprise.
Sampras, known for his powerful serve in his playing days, hit 10 aces in the match compared to Federer's six and put up a good fight. But it was not enough.
"I feel a little disappointed," Sampras said. "But I made Roger sweat a little bit tonight.
"I can still serve quite well but the hardest thing for me is movement," the former number one said. "I was a little careless up on the net and missed a few easy balls. But I think I will play well in the next match."
The balding Sampras broke him in the sixth game to forge ahead 4-2 after a deft drop at the net. But the world No 1 stepped up the pace to take the next four games and set with a clinical all-round display.
Sampras, who won 14 Grand Slams to Federer's 12, was equal to the task for much of the light-hearted match but committed several unforced errors and unable to reproduce the pace he generated in his heyday.
"When I found my range, Pete missed a few too many shots," Federer said. "I was maybe lucky to win the first set. Then I got on a roll and started to relax. I enjoyed the match very much."
The Swiss looked like running away with the second set as he claimed four of the first five games before Sampras won the sixth with the help of his booming serve. He allowed the American only one more game before wrapping up the match.
"Pete was one of my idols growing up and it's great to play him," Federer said later.
"It wasn't easy for me, it wasn't easy for him as he's been retired five years. I am number one and everyone expects me to win."
Sampras said he felt "pretty good".
"I made it competitive, which was my goal. Obviously Roger is the best player in the world and I retired five years ago. I am grateful that he invited me.
"I have no plans to come back from retirement. You have to come back for a reason. I just stay home and watch Roger win on television," the American added.