The 2021 Boston Marathon will be broadcast live from Boston, Massachusetts Monday, October 11 via NBC Sports Network television network, Peacock Premium and locally on CBS Boston WBZ-TV. 

From the event website:

• Global coverage of the Boston Marathon
• CBS Boston’s WBZ-TV is honored to once again be the exclusive local broadcast partner of the Boston Marathon, providing live wire-to-wire coverage of this world-class race for over 35 years.
• WBZ-TV offers a full range of Boston Marathon news, features, and athlete interviews, from the pre-dawn hours in Hopkinton to the celebration and emotion at the finish line in Copley Square…all to get viewers closer to Boston Marathon news and information as well as what the race means locally and around the world.
• Dedicated to serving the community, WBZ-TV is proud of its legacy as the exclusive broadcast partner to many of Boston’s signature events.
• For more about CBS Boston’s WBZ-TV, go to www.cbsboston.com.