The 37-year-old American arrived wearing a grey suit at the club while Federer and Andy Roddick were knocking up ahead of the men's singles final. Sampras was welcomed by officials at the players' entrance at the All England Club.
He was also greeted by women's champion Serena Williams and exchanged words before entering the Millennium Building at the club.
Sampras entered the Royal Box with Roddick leading 2-1 in the opening set, waved to acknowledge the crowd's applause and took his place in the front row, a few seats away from other former champions Bjorn Borg and Rod Laver.
Sampras had not returned to the club since his second-round exit against unseeded Swiss George Bastl seven years ago, with reports suggesting the multiple champion had been upset at being scheduled to play on Court Two.
Federer needs to beat Roddick in Sunday's final to move past the record of 14 grand slam victories he shares with Sampras.
Sampras won the Wimbledon title three straight years from 1993 before winning it four times in a row from 1997.
The American retired after winning his 14th grand slam title at the 2002 U.S. Open.
Photograph: Stefan Wermuth/Reuters