Ireland won a nerve-jangling final match against France 22-20 to finish ahead of England on points difference and secure a second title in 42 years.
Tuilagi came off the bench to score England’s sixth try in their 52-11 victory over Italy in Rome.
He made his return from a shoulder injury for Leicester Tigers at Newcastle Falcons at the start of March and Tuilagi’s appearance at the Stadio Olimpico was his first for England since last season’s Six Nations campaign.
Introduced from the bench alongside Tigers teammate Tom Youngs in the 54th minute, Tuilagi broke Leonardo Sarto’s tackle to score next to the posts 13 minutes into his return.
Mike Brown scored two first-half tries and there were scores for Owen Farrell, Jack Nowell, Mako Vunipola and captain Chris Robshaw. Farrell landed all seven conversions and a penalty.
The result left England’s Six Nations fate in the hands of France, who entertained Ireland at Stade de France later on Saturday.
A France victory would have crowned England champions for the first time since Martin Johnson led the Red Rose to the Six Nations in 2011, while a win for Ireland, in Brian O’Driscoll’s last international, would see them celebrate a first title since 2009.
France took an early 6-0 lead but fell 12-6 behind to tries by Jonathan Sexton and Andrew Trimble. But France retook the lead through Brice Dulin’s converted try and held a one-point advantage at the break after Sexton missed a simple penalty right on half-time.
Sexton scored his second try after the break and Sexton stretched the lead with a 53rd-minute penalty. But Dimitri Szarzewski’s try nine minutes later closed the gap to two points and set up a rousing finale.
France had Damien Chouly’s effort two minutes from time ruled out for a forward pass and gutsy Irish defence proved enough in the end.