The producer will offer his rememberances along with the actor's widow, Deborah Lin Gandolfini
Those in attendance included Gandolfini's former castmates Jamie-Lynn Sigler, Michael Imperioli, Aida Turturro and Vincent Curatola.
Time Warner Chairman Jeff Bewkes and New Jersey Gov. Chris Christie were also at the service at the Cathedral Church of Saint John the Divine, one of the city's largest churches. It began at 10 a.m. EST.
Gandolfini died last week of a heart attack at the age of 51. He was vacationing in Italy.
In addition to collaborating with Chase on the HBO crime series, the pair reunited last year for the music drama "Not Fade Away."
The actor's widow Deborah Lin Gandolfini and family friends Thomas Richardson and Susan Aston will also offer remembrances.