Hearts have launched a search to find a new manager as they bid to arrest their alarming decline down the Scottish Premier League table.
Frail joined the Hearts coaching staff in October 2004
Assistant coach Stephen Frail and sporting director Anatoly Korobochka have been in charge this season but the club have slipped to 10th place.
While the search takes place, Frail will become caretaker manager and have full control over first-team affairs.
"The board has begun a search for a new manager," said a club statement.
"The manager, who will have full responsibility for team selection, will be an experienced football manager and will preferably have experience of management in British football.
"The new manager will work with Anatoly Korobochka and Stephen Frail."
Frail and Korobochka have led Hearts since Valdas Ivanauskas left the club in March last year.
But there has been confusion as to who is picking the team, with Frail admitting in the past to having little input in the process.
Managers John Robertson, George Burley, Graham Rix and Ivanauskas have all been and gone since the arrival of Vladimir Romanov as majority shareholder.
Hearts are now just two places and 10 points ahead of basement club Gretna.
"The board of directors of Hearts acknowledges it is not acceptable for Hearts to be in its current position in the league," added the club statement.
"The new manager's task will be to drive the club forward on the playing side to fulfil the club's ambitions."