"While Singapore quietly climbed the ranks, the U.S. passport has fallen down since President Donald Trump took office," Arton Capital said in a statement. Turkey recently revoked visa-free status to American passport holders on the back of a diplomatic row.
Germany ranked second, followed by Sweden and South Korea in third place. Meanwhile, Japan and the U.K. were among the nations tied in the fourth tier.
Earlier this year, Arton Capital's index showed Singapore and Germany tied for first place but the city-state was propelled to the lone number one spot after Paraguay recently removed visa requirements, Arton Capital said.
"This is a testament of Singapore's inclusive diplomatic relations and effective foreign policy," Philippe May, managing director of Arton Capital's Singapore office, said in a statement.
Historically, the most powerful passports have mostly been European, according to the index.