The Sky Bet League One side have lost six of their last seven matches in all competitions, culminating in a 2-1 home defeat to Notts County in the Johnstone's Paint Trophy on Tuesday night.
Wilcox, who took over last December following a spell as caretaker boss, led the Iron to promotion last season having finished runners-up to Chesterfield in League Two.
He also enjoyed a record-breaking 28-game unbeaten run for a manager's first spell in charge, surpassing a feat set 1 25 years ago
However, he had come under increasing pressure in recent weeks with the club winning just two of their 11 league games to sit second-bottom
A statement on the club's official website, www.scunthorpe-united.co.uk read: " Scunthorpe United have today terminated the contracts of manager Russ Wilcox and assistant manager John Schofield with immediate effect
"The club would like to place on record their thanks to Russ and John for their efforts, but in particular to Russ for leading the Iron into League One.
"Andy Dawson will take charge of Saturday's game at Gillingham, assisted by Tony Daws."
Source : PA