Cruise showed up in the middle of a news conference Monday that he hadn't been expected to attend. The premiere of "Mission: Impossible III" was scheduled later that night.
"My mission impossible was to be here today," the 43-year-old actor told reporters. "I didn't want to come. My daughter was just born and I didn't want to leave her and her mother."
His daughter Suri was born Tuesday in Los Angeles. She is the first child for Cruise and Holmes, 27. Cruise has a son and daughter from his marriage to ex-wife Nicole Kidman.
"I'm going to be here for a few hours, and then I'm going to get on a plane and go back to Katie and Suri," Cruise said.
Cast members of "Mission: Impossible III" later delighted thousands of screaming fans by appearing on a podium in the packed square in Rome's historical center, Piazza del Popolo, where they were interviewed about the movie.
However, the warmest welcome was reserved for Cruise, who caused a wave of near-hysteria when he waved at the public and exclaimed, "Roma! Italy! Italia!"
He then climbed down several steps, picked up a white teddy bear someone had tossed in his direction and read the note attached to it.
"This is for Suri, we wish her lots of love and good things. Tom go always like you're doing now. Kiss to Katie," Cruise read.
He thanked the public for supporting him and his family.
"I also want to thank you for the warm welcome that you've given to my daughter Suri and my fiancee Katie, and I just love you all," Cruise said. "And I hope you enjoy this film because that's why I do it, I make them for you and I really want to entertain you."
In "Mission: Impossible III," superagent Ethan Hunt (Cruise) takes on an icy villain played by Philip Seymour Hoffman. Director J.J. Abrams, creator of TV's "Lost" and "Alias," has said he aimed to balance action with character interplay in the spirit of the television show on which the "Mission: Impossible" films are based.
Ving Rhames, Michelle Monaghan, Jonathan Rhys Meyers, Laurence Fishburne, Keri Russell and Maggie Q also star in the movie, which is scheduled to open May 5 worldwide.