The alleged accused was convicted in 2019 of trafficking around 1.5 kilos (3.3 pounds) of cannabis, Kokila Annamalai of local rights group Transformative Justice Collective told news agency AFP.
Singapore has one of the toughest anti-narcotics laws and as per the law, trafficking more than 500 grams of cannabis can result in the death penalty.
"A 36-year-old Singaporean man had his capital sentence carried out today at Changi Prison Complex," a spokesman for the city-state's prison service told AFP.
Singapore's Central Narcotics Bureau (CNB) released a statement saying that it would not reveal the name of the man in order to respect his family's wish for privacy.
"The person was accorded full due process under the law, and had access to legal counsel throughout the process," CNB added.
"A last-ditch appeal to review the case and stay his execution was dismissed on Tuesday", Annamalai said.
Despite growing calls for the city-state to abolish the death penalty and halt drug-related executions, Singapore presses that it is an effective impediment against trafficking.