Danum Eagles, promoted twice since 2014, have been relegated back to Division Three of the National League.
A 79-67 defeat in Saturday’s must-win clash at home to London Greenhouse Pioneers consigned the club to the drop.
Eagles were without leading scorer and rebounder Mathew Martin and missed his presence on court.
Head coach Bob Martin said: “It has been a very hard season.
“We must not forget what we have done in three years. We went through three divisions.
“I’m very proud of all the players. Doncaster Danum Eagles are respected all over the UK. We will be back.”
Eagles won back-to-back promotions after being elected to Division Four in 2014.