On the House floor, the speaker said members would not be recognized if they were not properly wearing their face coverings – and recognition would be withdrawn if masks were removed while a lawmaker was speaking, according to the official Twitter account of the chamber.
Recognition is when a representative is permitted to speak.
A spokesperson for Pelosi declined to comment further on the decision.
The majority of states have mask mandates in place, including the District of Columbia, but there is no uniform nationwide requirement. States are free to put their own restrictions in place to keep residents safe.
Meanwhile, President-elect Joe Biden has also suggested he would call for Americans throughout the U.S. to wear face coverings for 100 days to slow the spread of the virus once he takes office.
Biden has indicated he will work with state and local leaders to encourage them to enforce mask mandates.
This week, U.S. deaths related to the virus surpassed 300,000.