Fleetwood went ahead in the first half when striker Ellis Harrison beat Anthony Patterson with a low finish.
That prompted Sunderland boss Alex Neil to make a double substitution at half-time, as Jermain Defoe and Lynden Gooch were brought on.
Second-half goals from Elliot Embleton, substitute Luke O’Nien and Jack Clarke then gave the Black Cats a vital three points.
Fleetwood defender was then sent off for a foul on Ross Stewart three minutes from time.
Our chief SAFC writer Phil Smith has delivered his verdict on how each Sunderland player fared at the Stadium of Light:
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Second-half goals from Elliot Embleton, substitute Luke O’Nien and Jack Clarke then gave the Black Cats a vital three points.