Defoe has returned home following the death of his father.
The Football Association confirmed the news on Thursday morning, adding that the player is expected to return at some point and no replacement is being called up.
It is not known at this point whether Defoe will be back prior to Monday's Group D opener against France in Donetsk.
"England striker Jermain Defoe has returned home to England this morning following the passing of his father overnight," read an FA statement.
"Jermain will re-join the England Euro squad in due course. There will be no replacement player called in.
"We would ask all media to respect Jermain and his family's privacy at this difficult time."
Tottenham have also offered their sympathies to Defoe. "Everyone at the club sends their sincere condolences to Jermain and his family," the Barclays Premier League club said.