The 31-year-old has not played since injuring his shoulder in the Guinness PRO12 final in May but is on the verge of a return.
Dempsey said: "He's gone well. He went through a good block of work last week in training and a couple of things to do in training today (Monday), but it all looks good.
"We're delighted to have him back on board. He's been excellent the whole way through pre-season. "It's been massively beneficial to have him around the club from the start of the season. [We are] really excited to have him back on board."
But Dempsey did also confirm Sexton's Ireland and club team-mate Rob Kearney would be out of action for a couple of weeks with a knee injury, while Rhys Ruddock and Fergus McFadden will also be assessed ahead of Friday night's game.
"We're hopeful that [Kearney] will be back before Europe," Dempsey said at the press briefing.
"He's strained his knee so he's in a rehab programme at the moment. It's gut-wrenching for him. He'd come back and he was like a new kid: re-energised, revitalised, back on the field, actually taking a lot of ownership in certain areas of our game, and moving really well. It's just so disappointing for him to get that knock.
"He's responded well to his initial rehab and we're hopeful that he'll be back sooner rather than later."
Guinness PRO12 Final 2017 Ticket Information: Fans can save up to 20% on selected tickets, and prices start at just €30 adults and €5 child, and be booked via www.ticketmaster.ie.
For further information visit http://www.pro12rugby.com/final
Guinness PRO12 Leinster News
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