1144 GMT December 07, 2019
The 19-year-old, who was the subject of summer interest from Manchester United, scored 13 goals last season as Dortmund finished second behind Bayern Munich, BBC Sport reported.
Sancho also scored in Dortmund's opening league game this term — Saturday's 5-1 win over Augsburg.
Signed from Manchester City in 2017, his previous deal ran until 2022.
Sancho, who was part of Watford's academy before joining City, made his England debut against Croatia in October 2018 and has six caps.