"We would like to thank Lloyd for his work and commitment to not only the Hawks organization but the city of Atlanta. He and his wife, Melissa, are tremendous people who have made a positive impact throughout the city," Hawks president and general manager Travis Schlenk said in a statement.
"We have high expectations for our team on the court and we believe by making this change now that we can have a strong second half of the season."
Atlanta appointed Nate McMillan as its interim head coach, the team announced, per The New York Times' Marc Stein. McMillan has previous head coaching experience with the Seattle SuperSonics, Portland Trail Blazers, and Indiana Pacers.
Although the Hawks acquired several notable free agents this past offseason - including Danilo Gallinari, Bogdan Bogdanovic, and Rajon Rondo - they've posted a 14-20 record in 2020-21 while dealing with multiple injuries.
Pierce, who took over as Atlanta's bench boss ahead of the 2018-19 season, coached the team during Monday's practice in Miami before being fired, according to The Athletic's Chris Kirschner. He earned a combined 63-120 mark in parts of three campaigns.