Bayern Munich forward Muller and Borussia Dortmund defender Hummels have not featured for their country since November 2018.
They were among the experienced players removed from coach Joachim Low's thinking in March 2019 as he plotted a new path forward following Germany's group-stage exit at the 2018 World Cup.
But the pair have been trusted with helping Germany enjoy a successful tournament at the rescheduled Euros, which will be Joachim Low's final tournament in charge.
Die Mannschaft face an extremely difficult group, having been pitted alongside world champions France, defending European champions Portugal and Hungary.
They start their Group F campaign against France at the Allianz Arena on June 15.