The men, Vahid Mazloumin and his assistant Mohammad Esmail Qassemi, were arrested in July and sentenced to death in October.
Mazloumin, nicknamed the "Sultan of Coins," and his team had a two-ton stockpile of gold coins. They were accused of forming a black market for gold with the goal of increasing its price on the traditional market. Mazloumin was arrested for acting as a speculator and Qassemi for "spreading corruption."
Amnesty International condemned the execution, as the men were not accused of lethal crimes, calling it a flagrant violation of international law.
"Use of the death penalty is appalling under any circumstances, but it is even more horrific given that these men were convicted after a grossly unfair show trial that was broadcast on state television," Philip Luther of Amnesty said.
Iranian leader Ayatollah Ali Khamenei approved a judicial request in August to establish a special court for financial crimes ahead of US sanctions that were scheduled for early November and expected to impair the economy.
On Tuesday, police in the capital said some 130 traders of illegal currencies have been arrested in the past days.
Iran "can solve its economic problems by correctly using its domestic resources," Khamenei said on Wednesday.