Murray, who made his only Test appearance against France in Bordeaux nine days ago, travels with fellow scrum-halves Eoin Reddan and Isaac Boss.
O'Leary was thought to be coach Declan Kidney's first choice in the position but has paid the price for his poor display in Saturday's 26-22 defeat by Les Bleus.
Leicester full-back Geordan Murphy travels to New Zealand, as does Leinster utility back Fergus McFadden, but there is no place among the 30 for winger Luke Fitzgerald.
Murphy's hopes of inclusion looked dashed after he started the second string's victory over Connacht last Thursday.
At 33, the Leinster captain's Test career seemed over only for a foot injury to Felix Jones, sustained against France on Saturday, to narrow Kidney's options.
Jones, who had played himself into contention during the summer series, has been ruled out for six weeks and Kidney has opted for Murphy to supply support to first choice full-back Rob Kearney.
Alongside O'Leary, Fitzgerald is another big-name casualty who has also suffered because of a loss of form.
Fitzgerald played well as a second-half substitute against France at Aviva Stadium, but it was not enough to convince Kidney he should travel.
McFadden's ability to cover wing and centre has strengthened his claim to a spot among the 30.
Most of the squad, which is led by Brian O'Driscoll, picked itself with a 16-14 split between forwards and backs.
Only four props will travel with Tony Buckley securing the last available place, beating off competition from John Hayes and Marcus Horan.
Donnacha Ryan travels as the fourth lock but also offers back row cover, while Stephen Ferris features after making his first appearance since January on Saturday.
Andrew Trimble's fine form during the summer is rewarded and his rival wing Tommy Bowe is present despite not having played this month because of a foot injury.
Ireland squad for the Rugby World Cup: R Best (Ulster), I Boss (Leinster), T Bowe (Ospreys), T Buckley (Sale), T Court (Ulster), S Cronin (Leinster), L Cullen (Leinster), G D'Arcy (Leinster), K Earls (Munster), S Ferris (Ulster), J Flannery (Munster), C Healy (Leinster), J Heaslip (Leinster), R Kearney (Leinster), D Leamy (Munster), F McFadden (Leinster), G Murphy (Leicester), C Murray (Munster), S O'Brien (Leinster), D O'Callaghan (Munster), P O'Connell (Munster), B O'Driscoll (Leinster, capt), R O'Gara (Munster), E Reddan (Leinster), M Ross (Leinster), D Ryan (Munster), J Sexton (Leinster), A Trimble (Ulster), P Wallace (Ulster), D Wallace (Munster).
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