A hard fought encounter was settled thanks to Catley's second half spot kick, after midfielder Hayley Ruso was adjudged to have been pushed by Ireland's Marissa Sheva.
Despite the opening defeat, Ireland's spirited performance still leaves cause for optimism.
Vera Pauw's side almost snatched a late equaliser, when Megan Connolly's 90th minute free kick deflected inches over the bar, while Australian keeper MacKenzie Arnold produced a smart save from Irish captain Katie McCabe late on from an Abbie Larkin cross.
Ireland have to recover from this defeat, when they take on Canada on Wednesday in Perth.
