The second shot on goal came just before halftime but Katrina Gorry's long-range effort was easily gathered by Courtney Brosnan in the Ireland goal.
Australia came out with more intent after the break and the half was only seven minutes old when Kyra Cooney-Cross sent the ball looping into the box and Ireland forward Marissa Sheva shoved Raso to the ground.
Catley gave Brosnan no chance with the penalty, striking the ball with her left foot firmly into the top corner of the Ireland net.
The penalty appeared to ease the Australian nerves and Mary Fowler, who had replaced Kerr up front, almost immediately stormed forward and lashed a shot high over the bar.
Australia, however, held on to make a winning start to a tournament in which they feel they can be genuine contenders after wins over England, Spain and France this year.
Persons:
Steph Catley, Joy SYDNEY, Sam Kerr, Kerr, Catley, Hayley Raso, Katrina Gorry's, Courtney Brosnan, Kyra Cooney, Cross, Marissa Sheva, Raso, Brosnan, Mary Fowler, Caitlin Foord, Megan Connolly, Katie McCabe, Mackenzie Arnold, Louise Quinn, Nick Mulvenney, Peter Rutherford
Organizations:
Soccer Football, FIFA, of Ireland, REUTERS, Australia, Ireland, England, Thomson
Locations:
New Zealand, Australia, of, Sydney, Ireland, Auckland, Spain, France