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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1. Anthony Patterson - 6
Didn’t have much to do in terms of saves but claimed a couple of set pieces and distribution was decent. 6 Photo: JPI Media
2. Carl Winchester - 5
Not quite at his most incisive, trying to break forward but not quite finding the quality with his final ball. Plenty of industry, as ever. 5 Photo: JPI Media
3. Bailey Wright - 5
Did the bulk of his defensive work well though Sunderland were fortunate to get away with gifting a couple of good chances to Long on the break. 5 Photo: JPI Media
4. Dennis Cirkin - 5
Rarely troubled defensively but wasn’t able to set his team away in possession, in the way Callum Doyle often does from that area of the pitch. 5 Photo: JPI Media