Iowa (5-1) will play in the championship game Friday night against San Diego State or Creighton.
Joe Wieskamp had 16 points and six rebounds for the Hawkeyes, and CJ Fredrick scored 10. His 3-pointer off a broken play as the shot clock expired put Iowa up 64-59 with 1:29 left. He followed that up with two free throws with 1:07 remaining to put it away.
Iowa was 11 of 27 (41%) from behind the arc as Wieskamp hit four 3s.
Kevin McCullar fouled out for Texas Tech with 4:23 left, and Holyfield played with four fouls for the last 8:01.
Iowa opened a 36-21 lead in the first half, its largest of the game, before the Red Raiders scored the last five points of the period.
Iowa: Plays for the Las Vegas Invitational title against the winner of the San Diego State-Creighton game.
Texas Tech: Faces the loser of San Diego State vs. Creighton.