The game at the One Call Stadium was due to take place on Saturday night but it has been called off due to concerns raised by the Nottinghamshire Police.
A statement on Birmingham's official website read: "Birmingham City regret to inform supporters that tomorrow's pre-season fixture at Mansfield Town has been cancelled.
"Following a renewed risk assessment by Nottinghamshire Police last night, safety concerns were raised by the authority and, as a result, the level of police resources deemed necessary to stage the fixture has meant that it is now not financially viable for either club to proceed.
"Both clubs are disappointed that this decision was taken at such a late stage."
Birmingham's next game will now be on Tuesday, when they will travel to Meadow Lane to take on Notts County.