Philadelphia placed the veteran defenseman on unconditional waivers for the purpose of terminating his contract, general manager Chuck Fletcher announced Saturday.
The 32-year-old MacDonald contributed only nine points in 47 games this past season. He has one year remaining on his contract at a cap hit of $5 million, according to CapFriendly.
He signed a six-year, $30-million pact with the Flyers in 2014.
MacDonald spent parts of the last six campaigns with Philadelphia after beginning his career with the New York Islanders.
The NHL's first buyout period opened Saturday. It runs until June 30.