The 33-year-old missed Leinster's RaboDirect PRO12 semi-final victory over Glasgow last Saturday after undergoing minor knee surgery.
O'Driscoll, who has winners medals from 2009 and 2011, had said earlier in the week: "You'd want to have a limb falling off really to not play in the Heineken Cup final."
And the Ireland centre has returned to the Leinster starting line-up along with full-back Rob Kearney, who has overcome a back problem.
"Brian trained fully yesterday, he trained well, he is in good shape and he will play tomorrow," Leinster coach Joe Schmidt said after today's captain's run at Twickenham.
"Rob had a run today, he is feeling comfortable and we are confident he will be out there as well tomorrow. I would say those two guys are pretty much 100%.
"There is no medical reason why they wouldn't be playing - and it's pretty hard for me to stop them if that's the case."
The all-conquering Leicester team of 2001 and 2002 are the only team to have successfully defended the Heineken Cup title.
Leinster not only have the opportunity to match the Tigers' feat but establish their own Dublin dynasty on the Heineken Cup with a third triumph in four years.
"When we won against Leicester (in 2009), Leinster had been going through a tough period for 10 or 12 years and there was a feeling of relief more than anything else," said captain Leo Cullen.
"Last year against Northampton was strange. It couldn't have gone much worse for us in the first half (as Leinster fell 22-6 down) and the turnaround was so dramatic it was amazing.
"When you experience success it makes you more greedy and you want to experience those feelings all over again."
Ulster, who have been through difficult times of their own, are back in the final for the first time since they were crowned European champions in 1999.
Tomorrow's clash will be the pinnacle for coach Brian McLaughlin and for hooker Rory Best, who have spearheaded Ulster's transformation into a European powerhouse.
"A number of players have come through a lot at Ulster, a lot of players are born and bred and there is something special playing in a final for Ulster," Best said.
"Brian has hammered that home in his time at Ulster and every signing has bought into that. That is what has made us such a close team.
"It would be that bit extra special because Ulster rugby are so special to so many of us."
Leinster are the odds-on favourites but Ulster have claimed some mighty scalps on their route to Twickenham, most notably Clermont Auvergne, Leicester and Munster.
While the title is on the line, Schmidt and McLaughlin have their own little wager riding on tomorrow's result.
"Brian is a super fella," said Schmidt.
"He texted me before the Clermont semi-final to say good luck. He texted after and we agreed that whoever loses would shout a couple of pints afterwards.
"Inevitably, if you are playing for a guy who is a top notch fella and a guy who has invested heavily in a team, they will try to do their very best for him.
"We have worked hard to earn the tag of favourites but the reality is it will mean nothing on the pitch."
Ulster's hopes have been boosted by the return of loose-forward Chris Henry and prop John Afoa to a pack that was dominant in the semi-final victory over Edinburgh.
Henry missed Ulster's semi-final win against Edinburgh with an ankle injury while prop Afoa returns to the side after serving a four-match suspension for a dangerous tackle.
Paddy Jackson is retained at fly-half ahead of London Irish-bound Ian Humphreys for what will be only his second Heineken Cup start for Ulster.
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