Nick Carter on stage at Irving Plaza
Michael Stewart/Getty
Members of the mostly-female audience held up pink paper hearts in honor of Leslie, a gesture Carter acknowledged during the show.
Laura Codd, the fan who made the hearts, said they were also meant to thank Carter for not canceling the show.
"I made 100 of them and passed them out to the crowd ... to show we love him and support him and we appreciate him still coming out and performing tonight," said Codd, 26.
For the majority of the concert, Carter seemed upbeat, flirting with the crowd and cracking jokes.
But later in the performance, after returning to the stage following a short break, he used the song "Falling Down" to pay tribute to Leslie.
"I've never done this before and I never thought I'd ever have to, but I'd like to dedicate this song to my sister," he said.
As he introduced the Backstreet Boys hit "I Want It That Way," Carter told the crowd, "Let's celebrate her life."
A friend of Carter's who attended the show from New Jersey said he was surprised Carter had decided to forge ahead with his tour amid reports that Leslie, 25, suffered an apparent overdose.
"He said he didn't want to talk to anyone before the show, but to make sure I come backstage after," the friend said. "He hasn't talked to me about it yet but he seems fine."
