AFC Bournemouth lost £15.3m in the financial year ending July 2013, during a season that saw them promoted to the Championship for only the second time in the club's history.
The losses have increased hugely from the £3.4m loss they posted for 2011-12.
The Cherries' Russian owner Max Demin helped ease the financial burden with a loan of £8.7m, according to accounts filed at Companies House.
Bournemouth also owe a company controlled by Demin £7.5m, which is due by 5 October this year.
In total, their net debt is just over £15.5m, up from £7.3m, although turnover did increase by just over £1m to £5.1m.
In their directors' report, the club's holding company AFC Bournemouth Limited say: "The club's future strategy is to become sustainable and forward-looking, implementing strategy that minimises both risk and exposure.
"One of the key risks affecting the company is the achievement of playing success in order to maintain the club's Championship status."
The report went on to admit that "football wages continue to be the highest expense for the club".
Bournemouth have enjoyed a great season in the Championship, and are well on course for a top half finish.