A spokesman of the board said that the chairman, Shaharyar Khan had approved a request from the tour selection committee to send Rahat for the mega-event.
"Rahat will be proceeding to Australia on the recommendation of chief selector, Moin Khan," he said.
The inclusion of Rahat means that allrounder, Bilawal Bhatti will be flying back home after a nightmarish match against New Zealand in the second one-day international this week where he conceded 93 runs.
Rahat, 26, who has taken 31 wickets in 11 tests, has played just one 50-overs match way back in June, 2012 against Sri Lanka and went wicketless. He is considered more of a test bowler.
Junaid, Pakistan's most telling bowler in recent times, was ruled out of the World Cup after initially being named in the World Cup squad.
After recovering from a knee injury in January he was hit by a hamstring injury during practice just before the team left for New Zealand.