The hosts rallied and clawed their way back into the game with a try four minutes later, but the Magners League champions held on to a slender two-point advantage at the interval.
The visitors raced out of the blocks after half-time and Gary Brown gathered a delightful 46th minute cross-field kick and passed to the supporting Felix Jones and took the return catch to score an effort which was converted by Nacewa who assumed kicking duties.
On 51 minutes, a break on halfway from Nacewa, where the former Auckland Blues star beat several defenders, concluded in an offload to prop Jamie Hagan and the former Gormanston College man crossed over.
Eight minutes later Simon Keogh gathered a bouncing ball from another clever cross-field kick, this time from Ireland international Luke Fitzgerald, to add his name to the score-chart. Nacewa, who reverted to out-half on the interval, again added the points.
With ten minutes to go former Leinster Under-20 captain and second row Conor McInerney, benefited from a wonderful take by Devin Toner, and a strong maul by the pack to cross over, though his conversion was missed by substitute Kyle Tonetti.
Tonetti would later make amends by adding to a Fitzgerald effort in the closing minutes after replacement prop Stan Wright offloaded to Kevin McLaughlin who fed McInerney who found Enniskerry man Fitzgerald who ran in to out-pace the defence.
*Leinster will face Treviso on Saturday evening (KO: 8.30pm local time)
LEINSTER POINTS: I. Nacewa (1 try, 2 conversions), G. Brown / J. Hagan / Simon Keogh / C. McInerney / L. Fitzgerald (1 try each), J. Sexton (1 conversion), K. Tonetti (1 conversion)
LEINSTER: Isa Nacewa (Brian O'Driscoll, 62); Gary Brown (Girvan Dempsey, 62), Eoin O'Malley (Luke Fitzgerald, half-time), Fergus McFadden (Kyle Tonetti, half-time), Simon Keogh (Fergus McFadden, 62) (Eoin O'Malley, 72); Jonathan Sexton (Felix Jones, 30), Chris Keane (Paul O'Donohoe, 51); Cian Healy (Ronan McCormack, half-time), Brian Blaney (John Fogarty, half-time), Stephen Knoop (Jamie Hagan, half-time) (Stan Wright, 62); Trevor Hogan CAPTAIN (Malcolm O'Kelly, 55), Cameron Jowitt (Devin Toner, half-time); Kevin McLaughlin (Conor McInerney, half-time), Seán O'Brien, Stephen Keogh (Kevin McLaughlin, 62)