Commenting on the appointment Cullen said, "Isa made a superb contribution to the club on his return last season. He stepped up brilliantly in Kev's absence and then just grew into the role as the season went on.
"He is a perfect role model for the younger players but is also held in the highest regard by the senior members in our squad. He has a special connection with this club and with the supporters and we all look forward to seeing him back in action."
The former Fiji international scored nine tries in 23 games upon his return to Leinster colours last season but missed out on a place in the Guinness PRO12 Final against Connacht due to an arm injury.
Speaking about the appointment and the injury that ended his season the 34 year old back said, "I'm delighted to be appointed captain again. This club means a lot to me and my family and I'm looking forward to the season now and to leading the lads again.
"The body feels great. It was definitely worst case scenario in terms of how the season ended but the beauty of the timing of the injury is that I was here for the whole of the off-season and the planning of the pre-season. That included the review of the season, what went well, what needs to be better. So the body is in great shape. It's been a good exciting pre-season and it's been great having Charlie Higgins here. A new voice adding to the club."
With Gloucester Rugby playing Leinster this Saturday in Tallaght Stadium (Kick Off: 3.00pm) in the second of the Bank of Ireland Pre-Season Friendlies, Nacewa also took time to acknowledge the supporters that made the trip to Navan for the Ulster game on Saturday and looked forward to the game against the European Challenge Cup champions from two seasons ago.
"It was great support for a pre-season game in Navan. I don't think they could have fitted any more into the ground to be honest! It was a great atmosphere.
"This Saturday in Tallaght Stadium will be another opportunity for the young lads to step up against Gloucester and to create some further competition in the lead up to the Treviso game on the 2nd September. So everyone is looking forward to it and to running out in front of those supporters again."