Fort Bend County Judge KP George ordered Tuesday all retail businesses in the county to make employees and customers wear masks inside.
Commercial entities are responsible for enforcing the ordinance and can be fined $500 per infraction.
The order takes effect at midnight on June 25.
The cities of Houston, Galveston, Katy and La Marque have also implemented mask rules this week with the number of coronavirus cases spiking in Texas.
Texas has now reported 11 consecutive days of record-high hospitalizations for the coronavirus. Monday saw nearly 3,800 new hospitalizations per the Texas Department of State Health Services' data.