Faldo, who turned 50 last week during the British Open at Carnoustie, shot a 3-under 68 at the Muirfield Golf Club to tie Gordon Brand Jr., Nick Job and Dave Stockton for the top spot.
It was only the third competitive round of the year for Faldo, who won both the British Open and Masters three times during his under-50 career. He missed the cut at Carnoustie last week and admitted he did not expect to play well in the Senior British Open.
"I was very surprised," he said. "I was trying to do the best I could, trying to find a routine, and I was able to do it. And that scared me. I didn't know what to do."
After making a bogey at the opening hole, Faldo ran off three straight birdies. He finished his round by hitting his 6-iron approach to within three feet of the pin at 18, and that birdie putt lifted him into a tie for the lead.