The nearly 6-ton (6-metric ton) ball was raised Sunday to the top of a 130-foot (40-meter) pole at One Times Square.
The dry run is designed to make sure everything goes according to plan for the annual ball drop.
Jeff Straus, president of Countdown Entertainment, says that hasn't always been the case. He recalls a slight snafu in 1995 in which the ball was three seconds late.
He says a rehearsal is needed to ensure a timely ball drop.
The ball will light up at 6 p.m. Monday and begin to drop at 11:59 p.m. during the final seconds of 2018.
This story has been corrected to show that the spelling of a source's name is Jeff Straus, not Jeff Strauss.