Sanchez, who was the first woman to occupy the role, will return to her prior post as a lawmaker in the Senate, which she left after Lopez Obrador took office in 2018.
In a video posted on Twitter, the president presented Lopez as his "friend, countryman and close companion."
"We are satisfied with this decision and welcome (Sanchez) back," the ruling party's Senate leader Ricardo Monreal said in a statement. (Reporting by Anthony Esposito and Adriana Barrera; Writing by Anthony Esposito and Daina Beth Solomon; Editing by Rosalba O'Brien)

epa01536557 Players take their positions at the start of the millenial Aztec Ball Game at Zocalo square in Mexico City, Mexico, 30 October 2008, as part of the celebrations of the Day of the Dead. The playground is an exact real size replica of the one the Aztecs had in the middle of their city Tenochtitlan. EPA/MARIO GUZMAN