Sanders attracted over 28,300 people on Sunday afternoon, according to the campaign and a production company helping to plan the event.
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This total was higher than the campaign's previous record of 28,000 in Portland, Oregon, in August 2015, NBC News reported.
"In case you haven't noticed, there are a lot of people here this afternoon!" Sanders bellowed to cheers as he took the stage after veteran actor Danny DeVito glowingly introduced him.
Mega-rallies have been a staple of Sanders campaign since last summer, but only in the past few weeks has he brought show-of-strength events to New York City.
By March end, Sanders drew about 18,000 people to the South Bronx, according to the campaign.
Last week, more than 27,000 people showed up to hear him at Washington Square Park.
On Monday - the night before the all-important New York primary - another large crowd is expected in Long Island city.