The event was the Al Smith charity dinner which has a long tradition of inviting presidential candidates to be part of the annual fundraiser for Catholic charities.
Harris was the first such candidate, Democrat or Republican, in decades to turn the invitation and instead sent a video while she campaigned in Wisconsin.
Trump took advantage of her absence to call her decision "deeply disrespectful."
““If you really wanted Vice President Harris to accept your invitation, I guess you should have told her the funds were going to bail out the looters and rioters in Minneapolis and she would have been here, guaranteed,” said Trump, urging Catholics to vote for him in response.
“You better remember that I’m here and she’s not," he said.
In the video she recorded for the occasion, Harris appeared alongside comedian and actress Molly Shannon, who reprised her long-running “Saturday Night Live” character Mary Katherine Gallagher, an awkward Catholic schoolgirl.
The Alfred E. Smith Memorial Foundation Dinner is named for the former New York governor, a Democrat who was the first Catholic to receive a major-party nomination for president when he unsuccessfully ran for the White House in 1928.
The event has become a tradition for presidential candidates since Richard Nixon and John F. Kennedy appeared together in 1960. In 1996, the Archdiocese of New York decided not to invite then-President Bill Clinton and his Republican challenger, Bob Dole, reportedly because Clinton vetoed a late-term abortion ban.
