[15] Leaving Framingham, the runners enter the town of Natick, before passing through the "Scream Tunnel" at mile 12.

This area is lined by young women from the nearby Wellesley College who request kisses from runners, a tradition that has been in place for more than 100 years.

[15][18] The course is mostly downhill to the end, and passes through Boston College before entering Cleveland Circle and Kenmore Square, where there are many spectators.

[15][18] For the first time in Boston Marathon history, the elite men's race was started separately from the mass participation event.

[19] Kipruto pulled away from the leading pack with 3 miles (4.8 km) to go in the race, on Beacon Street,[20] and won by 49 seconds.

[25] Schär took the lead early on, and by half distance, she was five minutes ahead of Tatyana McFadden, her nearest competitor.

[25] On November 4, 2021, the University of California, Los Angeles Olympic Analytical Laboratory, an official World Anti-Doping Agency laboratory, found Diana Kipyokei of Kenya, who finished first in the women's division with a time of 2:24:45, tested positive for triamcinolone acetonide from her samples taken at the Boston Marathon.

Her representative sent a statement to the Athletics Integrity Unit stating she had been injected with the prohibited substance by David Njenga of Roybey Chemists on August 3, 2021, at the Uasin Gishu County Hospital in Eldoret, to treat a tendonitis injury from the Prague Marathon after three visits to the hospital on June 5 and July 14, 2021.

On December 7, 2021, the Athletics Integrity Unit announced after her representative's statement that she was under formal investigation for doping charges after a positive test.

On February 8, 2022, she was interrogated by the organisation, where she admitted two injections of the prohibited substance by Dr. Njenga occurred in September 2021.

On December 19, 2022, the six-year suspension went into effect, including formally being disqualified from the 2021 Boston Marathon by the Athletics Integrity Unit.