The Titans had been expected to build on their impressive 2021 season — when they reached the playoffs and were one pass away from defeating the Roosters to make the second week of the finals — but have flat lined this year.
They have lost 11 of their past 12 matches and are bottom of the NRL ladder.
Holbrook took charge of the Titans in 2020, after a successful stint at St Helens which included a Challenge Cup final appearance and a Super League Grand Final triumph over Salford.
He guided the Titans to 9th in 2020, which was a considerable bounce after they had claimed the wooden spoon in 2019.
Holbrook has won 22 of 61 matches at the Gold Coast during his tenure, though only three this year.
His impending exit adds to the list of NRL clubs that have dispensed with coaches in recent weeks, with Nathan Brown leaving the Warriors and Michael Maguire unwanted at the Wests Tigers.