The Leicester Tigers centre returned from a five-month injury absence to make just his second club appearance of the season in the win over Newcastle Falcons 10 days ago and has been training with the England squad since then.
England head coach Stuart Lancaster retained Tuilagi with his squad for training last week although he was not involved in the 23 for the win over Wales at Twickenham. Now he has stepped up and remains with the squad preparing at Pennyhill Park.
Tuilagi replaces Alex Goode as the only change in the 23 from the squad that faced Wales.
Tigers team-mate Tom Youngs is also retained in the squad, while colleagues Ben Youngs and Ed Slater have been released back to the club.
Head coach Lancaster said: “Every member of the squad has contributed to the cause over the last seven weeks and those not involved this weekend deserve massive credit for the way they have trained and pushed hard for places. There will be opportunities down the line, not least on the tour to New Zealand, and they can further stake their claims for that trip with strong performances for their clubs.
“Manu trained well with us last week and today and is up to speed with the way we want to play. Alex Goode has done well for us off the bench and is naturally disappointed, but we believe Manu, with the power and physicality he can bring, is the right choice to be included in the 23 for this game.”
Saturday’s match is a 12.30pm kick-off (UK time) at the Stadio Olimpico and will be shown live on BBC TV.
David Attwood (Bath Rugby)
Dylan Hartley (Northampton Saints)
Tom Johnson (Exeter Chiefs)
Joe Launchbury (London Wasps)
Courtney Lawes (Northampton Saints)
Joe Marler (Harlequins)
Ben Morgan (Gloucester Rugby)
Chris Robshaw (Harlequins)
Henry Thomas (Sale Sharks)
Mako Vunipola (Saracens)
David Wilson (Bath Rugby)
Tom Wood (Northampton Saints)
Tom Youngs (Leicester Tigers)
Mike Brown (Harlequins)
Luther Burrell (Northampton Saints)
Danny Care (Harlequins)
Lee Dickson (Northampton Saints)
Owen Farrell (Saracens)
George Ford (Bath Rugby)
Jonny May (Gloucester Rugby)
Jack Nowell (Exeter Chiefs)
Manusamoa Tuilagi (Leicester Tigers)
Billy Twelvetrees (Gloucester Rugby)
Returning to Aviva Premiership clubs:
Chris Ashton (Saracens)
Brad Barritt (Saracens)
Freddie Burns (Gloucester Rugby)
Alex Goode (Saracens)
Matt Kvesic (Gloucester Rugby)
Ed Slater (Leicester Tigers)
Anthony Watson (Bath Rugby)
Marland Yarde (London Irish)
Ben Youngs (Leicester Tigers)