D'Arcy partners Brian O'Driscoll in a team which is unchanged from the side that defeated Leicester Tigers 17-10 in the recent quarter-final at the Aviva Stadium.
Eoin Reddan links up at half-back with the tournament's top points scorer, Jonathan Sexton (88 points), with Luke Fitzgerald, Shane Horgan and Isa Nacewa completing the back-line.
There are six Ireland internationals in a pack which includes skipper Leo Cullen and Ireland props Cian Healy and Mike Ross.
The fit-again Shane Jennings takes his place amongst a strong replacements bench for this sell-out encounter.
LEINSTER (v Toulouse): Isa Nacewa; Shane Horgan, Brian O'Driscoll, Gordon D'Arcy, Luke Fitzgerald; Jonathan Sexton, Eoin Reddan; Cian Healy, Richardt Strauss, Mike Ross, Leo Cullen (capt), Nathan Hines, Kevin McLaughlin, Sean O'Brien, Jamie Heaslip.
Replacements: Jason Harris-Wright, Heinke van der Merwe, Stan Wright, Devin Toner, Shane Jennings, Isaac Boss, Ian Madigan, Fergus McFadden.