The first lady is experiencing mild symptoms and will remain quarantined in her home in Delaware.
President Joe Biden was also given a COVID-19 test and the results came back negative.
"The president will test at a regular cadence this week and monitor for symptoms," the White House said.
The first lady had planned to start the new school year Tuesday at Northern Virginia Community College, where she teaches English and writing.
Due to her condition, she was working with school officials to arrange substitute teachers for her classes, communications director Elizabeth Alexander said
The first lady had traveled with her husband to Florida on Saturday to inspect the damage from Hurricane Idalia. The president then spent part of the Labor Day weekend at the Delaware beach house before traveling Monday to a union event in Philadelphia and then back to the White House.
FILE - US President Joe Biden and First Lady Jill Biden walk to the White House upon arrival on the South Lawn in Washington, DC, August 26, 2023, following a week long vacation in Lake Tahoe, Nevada.
The first lady is double-vaccinated and has received two boosters, according to a statement from her communications director last year.
The last time the 72-year-old tested positive for the virus was in August 2022. At the time, she was staying at a private residence in South Carolina.
The announcement comes amid rising COVID-19 cases and hospitalizations throughout the country, as several hospital systems have reinstated mask-wearing requirements for patients and staff.
The Associated Press and FOX News contributed to this report. This story was reported from Los Angeles.