The League Two side had only appointed former Ross County, Plymouth Argyle and Morecambe boss in June, but he paid the price for a run of nine wins, 15 draws and 13 defeats from his 37 fixtures in charge, sitting 12th in the table.
The Bantams chief executive officer Ryan Sparks, said: “On behalf of the board, it is with deep regret that we have come to the decision to part company with Derek Adams.
“A sustained period of consideration has led to this decision and it is felt that, with all things taken into account, the club must move in a different direction with regards to the role of first-team manager.
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“We would like to thank Derek for his efforts while at Valley Parade, and wish him the very best for the future.”
Assistant manager Mark Trueman will take caretaker charge of first-team affairs with immediate effect, starting with Saturday's match against Oldham Athletic.
Pereira signed at the Utilita Energy Stadium until the end of the season back in January, but hasn't featured yet due to picking up an injury.