Under the sanctions, US firms and individuals are banned from doing business with Mr Maduro.
The election of a constituent assembly on Sunday was held amid mass protests. At least 10 people were killed.
The US had previously warned that it would not recognise the election, with President Donald Trump vowing "strong and swift economic actions" if it went ahead.
Mr Maduro is only the fourth foreign leader to be blacklisted in this way joining an "exclusive club" that includes Syria's Bashar al-Assad, North Korea's Kim Jong-un, and Zimbabwe's President Robert Mugabe.