Fisichella poses in Ferrari team kit at the factory
Giancarlo Fisichella will drive for Ferrari for the rest of the 2009 Formula 1 season before taking a new role as their reserve driver in 2010.
The Italian, 36, will replace Luca Badoer as stand-in for the injured Felipe Massa for the final five races.
"It has always been an ambition," said Fisichella, who has been released from his contract with Force India.
Force India are yet to name a replacement for Fisichella with reserve driver Vitantonio Liuzzi the favourite.
Fisichella, who formerly raced for Minardi, Jordan, Benetton, Renault and Sauber, will begin his Ferrari career on home soil at the Italian Grand Prix on 13 September.
Ferrari team boss Stefano Domenicali confirmed the appointment saying: "We considered what could be his role inside the team in the near future, also taking this year's experiences into account. He will be the reserve driver in 2010.
"We have chosen Fisichella because we can expect him to make a valuable contribution in this final part of the season.
"He has shown, throughout his long career, that he is fast and competitive and we are therefore proud to be able to run an Italian driver in our home race."
Force India team principal Mallya had insisted on Tuesday that he would turn out his regular team for Monza.
But after extensive discussions with Ferrari, Mallya has agreed to release Fisichella from his contract, which was due to expire at the end of the season.
"For any Italian driver, a Ferrari race seat is a long-held dream and for Giancarlo it was no exception," Mallya said. "No-one should stand in the way of this.
"The agreement will secure Fisichella's long-term future with Ferrari and it would be incorrect to jeopardise this.
"We would like to stress that we have not agreed any financial settlement with Ferrari and would like to thank Giancarlo for all his help over the past one-and-a-half seasons and for our first world championship points."
Fisichella's parting gift to Force India was second place at the Belgium Grand Prix, handing the team their first podium and points in their second season in F1.
Even before his impressive performance at Spa-Francorchamps, the 36-year-old had been tipped to replace Badoer, who has struggled since his promotion from Ferrari reserve driver.
Badoer was drafted in to replace Massa, who suffered serious head injuries at the Hungarian Grand Prix, after legendary seven-time F1 champion Michael Schumacher was forced to shelve his comeback plans.
I hope I have helped Force India grow up and be on the right path to achieve their own ambitions
While Massa is targeting a return in 2010, the Italian team ran out of patience with Badoer, who qualified last at both the European and Belgian GPs.
While Kimi Raikkonen claimed Ferrari's first win of 2009 in Spa, his team-mate trailed in last, nearly 48 seconds slower than the driver in front.
"We wish to thank Luca Badoer for the team spirit he demonstrated in these circumstances," added Domenicali.
"It is a shame he was unable to show his true worth in these last two races, tackled under conditions which anyone would have found difficult."
Fisichella, a veteran of more than 200 grands prix, will be expected to be much more competitive as Ferrari prepare to race in front of their enthusiastic home fans in Monza.
"I am grateful to Vijay Mallya for allowing me this opportunity," said Fisichella, a three-time race winner.
"For Vijay to have allowed it to become a reality is very generous and I hope in my turn I have helped Force India grow up and be on the right path to achieve their own ambitions."