Treasury Secretary Steven Mnuchin said the sanctions were used to target those undermining Hong Kong's autonomy, reports BBC.
"The United States stands with the people of Hong Kong," he added.
The development came weeks after China imposed a controversial national security law on Hong Kong.
The effort drew much criticism across the globe and critics said the law threatened Hong Kong’s freedoms.
Among those sanctioned are Hong Kong's police commissioner and several political secretaries.
The US Treasury directly accused Ms Lam of "implementing Beijing's policies of suppression of freedom and democratic processes."
"In 2019, Lam pushed for an update to Hong Kong's extradition arrangements to allow for extradition to the mainland, setting off a series of massive opposition demonstrations in Hong Kong," the US Treasury said in a statement.