Data compiled from MLBShop.com sales of Majestic jerseys since New Year's Day had Harper's No. 3 shirt topping the New York Yankees' Aaron Judge, Boston Red Sox's Mookie Betts and Los Angeles Angels' Mike Trout for first place on the list.
St. Louis Cardinals catcher Yadier Molina has the fifth most popular jersey, followed by Los Angeles Dodgers ace Clayton Kershaw, Chicago Cubs' Javier Baez, Milwaukee Brewers' Christian Yelich, Cubs' Anthony Rizzo and Atlanta Braves' Ronald Acuna Jr.
The official shirt of Cardinals newcomer Paul Goldschmidt is No. 11. San Diego Padres slugger Manny Machado, retired Seattle Mariners outfielder Ichiro Suzuki, Dodgers' Cody Bellinger, Cubs' Kris Bryant, Houston Astros' Jose Altuve, Astros' Alex Bregman, Red Sox's Andrew Benintendi, Yankees' Giancarlo Stanton and Braves' Freddie Freeman round out the top 20 in jersey sales.
Harper's Phillies jersey also set the professional sports record for most jerseys sold in the first 24 and 48 hours. Judge's nameless No. 99 has been the top seller in baseball in the last two seasons.
Trout's No. 27 has been one of the five most popular jerseys five times since making his MLB debut in 2012. He has appeared in the top 20 in every season.
Harper makes his Phillies debut against the Atlanta Braves at 3:05 p.m. Thursday at Citizens Bank Park in Philadelphia.