The Great Fitzgerald grants a boost to Fitzgerald's physical prowess that is directly proportional to the amount of money he spends. This allows him to have greater strength, speed, agility, and endurance beyond the normal human level. Notably, Fitzgerald throws off his cheques and states the amount of money he spends to activate his ability, though he can still "spend" some money for his ability by merely verbalizing his spent money. Moreover, distinguishing green markings appear throughout Fitzgerald's skin and garments, which signal that his ability is activated.
Activation of the ability is not restricted to Fitzgerald's own wealth, as he can use others' wealth, provided they "offer" it to him for his ability. Besides his money and cheques, the ability can also consume other items with corresponding worth to activate. For example, Fitzgerald's wedding ring worth at least $5,000 was spent for his ability that allowed him to survive falling from the Moby Dick.
Fitzgerald's ability-induced strength varies according to the financial amount he spends:
- 50¢: Fitzgerald can land a relatively strong punch on a target, though he claims that it is not that strong enough.
- $100,000: Fitzgerald is able to kick Atsushi Nakajima strongly enough for him to be thrown at the wall. He can also stop Ryunosuke Akutagawa's attack with his bare hands and even pull it towards him. He can also launch an opponent with a single punch.
- $500,000: Fitzgerald is able to counter Akutagawa's attacks, and he can also throw Atsushi easily with one arm. He is able to kick through a wall using a single leg.
- $500,000 wedding ring: Fitzgerald can survive a direct fall from a high altitude down to the ground.
- Remaining wealth: As his last resort, Fitzgerald's expenditure of his previously remaining disposable assets can block a pair of strong attacks. This also gives him superhuman agility, flexibility, and endurance.
- Louisa May Alcott's wealth: All of Louisa's money and assets allow Fitzgerald to defeat an entire gang.
- (Unspecified amount): After acquiring Manhasset Security, Fitzgerald once spent an unspecified amount for his ability on Tom Buchanan and blocked the latter's punch. It is also hinted that he might have broken Buchanan's fist.
- Physical Enhance: $50,000 (身体強化・五万ドル, Shintai Kyōka: Goman Doru?): Spending $50,000 on his ability, Fitzgerald can throw and puncture a fountain pen through his opponent's palm, which is left lodged on the wall due to its impact.
- It is implied that Fitzgerald's ability is activated during his cruise at the onset of the three companies conflict when he threw gun bullets with considerable strength and during his first meeting with Atsushi when he briefly clashed with him. However, if this were indeed the case, his distinctive green markings are missing in both scenes.
- The ability's reference work, The Great Gatsby, is considered by various academics as a notable work representing the Great American Novel. Though the list of candidates for the merit is dynamic and relative, other candidates on the list include works of the real-life counterparts of the in-series Fitzgerald's former co-members from the Guild, namely The Scarlet Letter by Nathaniel Hawthorne, Moby-Dick by Herman Melville, Adventures of Huckleberry Finn by Mark Twain, and The Grapes of Wrath by John Steinbeck.
- Interestingly, these works are the exact names of the abilities of their corresponding users in the series.