Dacey has been away with the Welsh set-up throughout pre-season, but now returns to the team as Head Coach Danny Wilson makes a total of three charges to his side.
Prop Craig Mitchell comes in at tighthead, with Taufa’ao Filise ruled out, to pack down alongside Dacey and loosehead prop Sam Hobbs.
The other change comes in the back line where Owen Jenkins takes the place of Tom James, who misses the trip to Ireland as he recovers from a foot injury.
Cardiff Blues sit at the top of the Guinness PRO12 standings after the bonus point victory over Zebre in the opening round of fixtures.
However, Wilson is under no illusions as to the challenge ahead as his team kick-off a run of four away trips to Irish provinces with the game against a Leinster side smarting from opening day defeat to Edinburgh.
“Leinster get a fantastic home crowd, they are well supported and they get momentum from the backing they enjoy so it should be a great atmosphere,” he said.
“Whichever way you look at it we go there as underdogs, even though we come off from a good win and they come off from a loss. But what a great place it would be to go and get a win.
“There are not too many changes to the side this weekend, for obvious reasons, because we had a good performance at home and set some records,” he added.
“We are missing a few players with bumps and knocks, but we are fairly settled and we go into the game with a little bit of momentum from the win and confidence. “
Cardiff Blues: 15 Dan Fish, 14 Aled Summerhill, 13 Tom Isaacs, 12 Gavin Evans, 11 Owen Jenkins, 10 Rhys Patchell, 9 Tavis Knoyle; 1 Sam Hobbs, 2 Kristian Dacey, 3 Craig Mitchell, 4 Jarrad Hoeata, 5 James Down, 6 Josh Turnbull, 7 Josh Navidi (c), 8 Manoa Vosawai
Replacements: 16 Ethan Lewis, 17 Thomas Davies, 18 Scott Andrews, 19 Lou Reed, 20 Ellis Jenkins, 21 Lewis Jones, 22 Gareth Davies, 23 Garyn Smith