Completing a hat-trick of comebacks, veteran Spaniard Pedro de la Rosa made his first appearance in three years as a fully-fledged racing driver when he tested the new Sauber.
The 41-year-old Schumacher, who last raced for Ferrari in 2006, took over from team-mate Nico Rosberg with an hour and a half remaining of the first test session of the new season at Valencia's Ricardo Tormo circuit.
With photographers and reporters crowding the pitlane, Schumacher guided the silver W01 car out onto the track where Massa had already racked up more than 60 laps.
The Brazilian, clearly back up to speed in the new Ferrari F10, was returning to competitive action six months after suffering life-threatening head injuries in Hungarian Grand Prix qualifying.
Within minutes, Schumacher was already lapping faster than Brazilian Rubens Barrichello, another former Ferrari team-mate, in the Williams. The lap times meant little, however, with refuelling banned this season and cars testing with varying fuel loads and specifications.
Rosberg, who completed 39 laps, said first impressions of the new car, an evolution of the Brawn that won both of last year's championships before the team was taken over by Mercedes, were very positive.
“It felt great, although difficult to compare because there are so many things different with the fuel and tyres,” added the 24-year-old, who has joined Mercedes after four years at Williams.
“To have him (Schumacher) here is fantastic,” he told reporters. “It has given me a little bit extra motivation I must say, from my point of view. Just that little touch extra.”
Britain's Gary Paffett gave the sleek-looking new McLaren its test debut, before world champions Jenson Button and Lewis Hamilton get their hands on it later in the week.
Poland's Robert Kubica made his Renault debut, after moving from BMW-Sauber, while Switzerland's Sebastien Buemi gave the new Toro Rosso a first run.