The left-handed pitcher from Germantown Friends School in Philadelphia was taken with the 27th pick in the first round.
Biddle, 18, is 6-foot-5 and weighs 225 pounds. He went 9-2 with a 1.06 ERA in his senior season. He struck out 140 in 59 1/3 innings, allowing just 21 hits and 29 walks. He went 5-0 with a 0.64 ERA as a junior, striking out 61 in 33 innings.
The area high school product has a fastball that reaches 94 mph and also throws a curveball, slider and changeup.
Biddle will be assigned to the Phillies' Gulf Coast League team in Clearwater, Fla.