The strumming of a Spanish guitar and the voices of Eydie Gormé and Los Panchos echoed throughout the hall as “Sabor a Mí” played on a loudspeaker. Hundreds of mourners made their way into Judson Memorial Church, near Washington Square Park in Manhattan.

Inside the sanctuary, all attention was front and center on an ofrenda, or altar, that was adorned with flowers and flickering votive candles. About a dozen portraits of the same women, the activist Cecilia Gentili, smiled out on the crowd.

While the loss of Ms. Gentili, who died on Tuesday at 52, could be felt throughout the crowded church, her impact reached far beyond its doors.

“Cecilia’s my mother,” said Oscar Díaz, an artist in Queens. “She’s an icon. She’s a legend in the trans, undocumented and sex-work community.”

In recent years, Ms. Gentili had branched out from her main calling: publishing a memoir, starring in a one-woman show and even appearing in several episodes of Ryan Murphy’s “Pose.” But on Wednesday night, she was remembered chiefly for her advocacy on behalf of trans people, the undocumented and others living on the margins.