The Blazers obtained the 6-9 Miles in a trade with the Cleveland Cavaliers in January, sending point guard Jeff McInnis to Cleveland.
The 22-year-old Miles played in 42 games, including 40 starts, with Portland, averaging 12.6 points, 4.6 rebounds and two assists per contest.
"We had identified Darius as a top priority this off-season," said Portland General Manager John Nash. "At his age, he not only represents the present, but the future of the franchise. Darius has worked hard in this off-season to build upon the success that he enjoyed under (Coach) Maurice Cheeks last year and we anticipate a tremendous season from him."
Miles originally was drafted by the Los Angeles Clippers in the first round (third pick overall) of the 2000 NBA Draft after a stellar prep career at East St. Louis (Ill.) High School.