Horton left in the first overtime period of Boston's 4-3 Game One loss to the Chicago Blackhawks on Wednesday with what was described as an upper body injury.
He practiced with the team on Friday and took part in the morning skate on Saturday ahead of Game Two scheduled for later that evening.
"I feel good. I'm going to be ready," said Horton. "I think I'm in, ready to go. I'm excited."
Julien confirmed Horton, who seven goals and 18 points in 17 playoff contests, would be on the Bruins' bench.
"He's in tonight. Feels good," said Julien. "He looked really good out there, the last two days.
"There's absolutely no reason he shouldn't play tonight."
Horton's return will be a big boost for the Bruins allowing Julien to keep what has been the playoffs' hottest line intact.
David Krejci, Milan Lucic and Horton have been on a tear through the post-season combining for 21 goals and 57 points.
(Reporting by Steve Keating in Toronto; Editing by Gene Cherry)