Duke's backcourt -- including Trevon Duival in its three-guard starting lineup -- combined to shoot 14 of 30 on 3-pointers.
It matched the second-most points for Allen this season and only his second outing above 20 in the last dozen games. The other came with 23 on Sunday at Georgia Tech.
Wendell Carter Jr. added 13 points and 13 rebounds and Duval provided 10 points for the third-place Blue Devils (21-5, 9-4 Atlantic Coast Conference).
Duke played for the second game in a row without freshman sensation Marvin Bagley III, a forward who leads the ACC in scoring and rebounding. He was held out with for what Duke officials called precautionary reasons with a mild right knee sprain.
Duval, a freshman guard, was back in the lineup after a one-game stint as a reserve for the Blue Devils, who had gone 1-2 in their past three road outings.
Justin Bibbs scored 15 points for Virginia Tech (18-8, 7-6), which was coming off Saturday's overtime victory at now-No. 1 Virginia.
Junior guard Justin Robinson, who led the Hokies in the scoring in the past three games with at least 20 points, scored just five. He left for several minutes with three fouls barely a minute into the second half.
Duke stretched its lead to 49-36 with less than 14 minutes to play. It was 56-39 with 11:30 remaining after Javin DeLaurier's dunk off Duval's pass on a fast break.
By halftime, Trent and Allen combined for seven 3-point baskets as Duke, which scored the final seven points of the first half, led 36-28.
Duke was charged with eight of the first half's 10 turnovers. The Blue Devils had only six first-half points in the paint.
Virginia Tech didn't attempt a first-half free throw, while Duke was 4 of 4 from the line.
The teams will meet again Feb. 26 in Blacksburg, Va.
--Field Level Media
Virginia Tech | Duke | |
Justin Bibbs 15 | Scoring | Grayson Allen 25 |
Justin Robinson 5 | Assists | Grayson Allen 6 |
Kerry Blackshear Jr. 4 | Rebounds | Wendell Carter Jr. 13 |
Kerry Blackshear Jr. 3 | Free Throws Made | Wendell Carter Jr. 2 |
Nickeil Alexander-Walker 4 | Steals | Gary Trent Jr. 3 |
Kerry Blackshear Jr. 1 | Blocks | Marques Bolden 2 |
Team | Points | FG% | 3PM-3PA | FTM-FTA | Assists | Rebounds | Blocks | Steals | Turnovers |
Virginia Tech | 52 | 42.9 | 7-20 | 3-4 | 13 | 18 | 1 | 6 | 10 |
Duke | 74 | 50.0 | 15-33 | 7-10 | 16 | 34 | 4 | 7 | 13 |