A Sutton United fan picked up £13,500 after betting on the National League side to stun Leeds United.
Ladbrokes say one of their customers staked £3,000 at 7/2 - for a £10,500 profit.
Sutton's 1-0 win over Leeds on Sunday capped a weekend of FA Cup shocks.
Wolves were victorious at Liverpool before Lincoln beat Brighton, Oxford stunned Newcastle and Millwall saw off Watford.
The odds on the five-fold were 3,948/1.
Ladbrokes spokesman Alex Donohue said: "This weekend proved the magic of the Cup is alive and well, with a string of sides defying the odds across the country.
"Lincoln and Sutton fans will be daring to dream and looking at the odds it isn't completely written off one of them makes Wembley for the semi-finals at least."
The draw for the FA Cup fifth round takes place on Monday at about 7.20pm. It will be shown live on The One Show on BBC One.
FA Cup betting odds from Ladbrokes
- Lincoln to win the FA Cup 300/1
- Sutton to win the FA Cup 750/1
- Lincoln v Sutton final 10,000/1
Who will go the furthest? (bets void if both out in next round)