Mookie Betts has worn number 21 to honor Roberto Clemente as part of MLB’s Roberto Clemente Day, not because he permanently changed his jersey number.

Quick Scoop: Why he’s wearing 21

On specific games in mid-September, MLB celebrates Roberto Clemente Day, a league-wide tribute to Hall of Famer Roberto Clemente, who is remembered both for his greatness on the field and his humanitarian work.

On those days:

  • Certain players are allowed to wear jersey number 21.
  • This includes Roberto Clemente Award nominees, past winners, and eligible players honoring Clemente’s legacy.

Mookie Betts has been a Roberto Clemente Award nominee, which is why he’s allowed to switch from his usual number to 21 for that special game.

So when you see Mookie Betts in 21, it’s not a random style choice — it’s a one-day tribute tied to Roberto Clemente Day and his nomination for the prestigious Roberto Clemente Award.

Extra context: why 21 matters

  • Number 21 is closely linked with Roberto Clemente, a Pirates legend and Hall of Famer.
  • MLB uses September 15 each year to celebrate his career and especially his off-field humanitarian impact.

TL;DR

Mookie Betts wears 21 on select days because he is a Roberto Clemente Award nominee and MLB lets those players wear 21 as a tribute on Roberto Clemente Day, honoring Clemente’s legacy and humanitarian work.

Information gathered from public forums or data available on the internet and portrayed here.