Trevon Duval poured in 19 points, while Grayson Allen and Gary Trent Jr. each finished with 16 points for Duke (27-7), which is the No. 2 seed in the Midwest Region. That trio of guards all sank four 3-point shots as part of the Blue Devils' 13-for-30 long-range shooting, while Bagley shot 10-for-14 from the field.
Coach Mike Krzyzewski extended his record for NCAA Tournament victories to 92.
Duke will meet seventh-seeded Rhode Island, an 83-78 overtime winner against Oklahoma, in Saturday's second round.
Roland Griffin had 21 points on 9-for-12 shooting off the bench, TK Edogi posted 11 points and Zach Lewis and Rickey McGill both had 10 points for 15th-seeded Iona (20-14), which lost in the tournament's first round for the third year in a row. All those came by double-digit margins, though this was the second-most lopsided of the program's 13 NCAA Tournament defeats.
Wendell Carter Jr.'s nine points and team-high eight rebounds contributed to Duke's superiority close to the basket.
Duke held a 53-39 halftime lead, bolstered by 61.8-percent shooting (21-for-34) from the field.
Iona picked up 15 fast-break points in the opening half, helping the Gaels shoot 16 of 29 from the floor.
The Blue Devils opened the second half with a burst, with Iona calling a timeout less than two minutes in.
Duke opened shooting 4-for-4 on 3-pointers (two each for Duval and Allen) for a 17-10 lead. Iona pulled even at 19-19.
Duke's 17-point lead was shaved to nine late in the first half, but Allen's 3-pointer at the horn helped stretch it again.
Iona was a surprise champion in the Metro Atlantic Athletic Conference Tournament. It averaged 79.8 points per game for the season prior to Thursday.
This was the first meeting between the programs.
--Field Level Media
Iona | Duke | |
Roland Griffin 21 | Scoring | Marvin Bagley III 22 |
Schadrac Casimir 6 | Assists | Grayson Allen 9 |
TK Edogi 9 | Rebounds | Wendell Carter Jr. 8 |
Roland Griffin 3 | Free Throws Made | Marvin Bagley III 1 |
Zach Lewis 2 | Steals | Wendell Carter Jr. 2 |
TK Edogi 1 | Blocks | Wendell Carter Jr. 1 |