Ferrari said Wednesday in a statement that the German had agreed to get back in the cockpit until Massa is fit to return. The next race is the European Grand Prix on Aug. 21-23 in Valencia, Spain.
"Though it is true that the Formula One chapter has long been closed for me, it is also true that for team loyalty reasons I cannot ignore that unfortunate situation," the 40-year-old Schumacher said. "But as the competitor I am, I also very much look forward to facing this challenge."
The 28-year-old Massa was hit in the helmet by a loose part from another car and crashed into a protective tire barrier at 120 mph during qualifying Saturday at the Hungarian Grand Prix.
The Brazilian received multiple skull fractures in the accident and doctors say he will not race again this season.
Massa took his first steps since the crash on Wednesday and was later scheduled to leave the intensive care unit of the AEK hospital in Budapest. He also received a visit from Ferrari chairman Luca di Montezemolo.
Ferrari said Schumacher will undergo a special training program in the coming days to determine whether he will be able to drive in Valencia. There are six races left in the season after the European GP.
"Thanks God, all news concerning Felipe is positive. I wish him all the best again," Schumacher wrote on his Web site.
Schumacher, who had 91 wins in 250 F1 races starts, still acts as a consultant for Ferrari. Since retiring in October 2006, Schumacher has raced occasionally in a motorcycling series but was injured in a crash in February.
Schumacher won his first two F1 titles with the Benetton team. He joined Ferrari in 1996 and won five straight from 2000-04.