The family of late Ground Zero responder and 9/11 victims advocate Luis Alvarez received a symbolic key to the city Tuesday — and a moving eulogy from fellow victims activist Jon Stewart.

“Luis Alvarez represented the quiet heroism of acting compassionately,” Stewart said at the solemn City Hall ceremony Tuesday. Stewart recounted how Alvarez, who was diagnosed with colorectal cancer linked to the three months he spent at the destroyed World Trade Center site, posted about his illness on Facebook and urged other responders to get medical help.

Mayor Bill de Blasio gave Alvarez’s widow Alaine Alvarez the gold-plated key in a velvet box for the fallen NYPD detective’s emotional plea on Capitol Hill in June to replenish the September 11th Victim Compensation Fund.

De Blasio noted that Alvarez, an ex-Marine, attended the hearing the day before his 69th round of chemotherapy.

Alvarez died from liver failure just weeks after his testimony — and shortly before Congress passed a bill permanently extending benefits to victims who were sickened by toxic fumes in the days and weeks following the Sept. 11, 2001 terror attacks.

“He would be very honored to receive this award today,” Alvarez’s oldest brother Phil Alvarez said at the event.