The decision gave the embattled Israeli leader a small boost at a time when he already is facing three separate criminal investigations in unrelated real-estate and political corruption cases. Olmert has denied any wrongdoing, but the investigations have cast a cloud over his efforts to restart peace talks with the Palestinians.
In a statement Tuesday, deputy state prosecutor Yariv Regev said legal officials determined "there is not enough evidence to support suspicions that would justify the opening of a criminal investigation" into two real-estate deals.
Olmert had been suspected of selling a Jerusalem home to a wealthy supporter for hundreds of thousands of dollars above market value. The other case surrounded suspicions that he bought a property in a trendy Tel Aviv neighborhood at a steep discount.
The decision does not end Olmert's legal troubles.
Earlier this month, Israel's attorney general ordered a criminal investigation into suspicions that Olmert acted improperly while he was trade minister earlier this decade.
The state comptroller, a watchdog agency, has alleged that Olmert steered a government grant to a friend and arranged improper political appointments.
Last week, Olmert was twice interrogated by police on suspicion he tried to rig the sale of Israel's second-largest bank in favor of two associates while he was finance minister.
Police are also looking into Olmert's involvement in another real-estate deal in which he is suspected of buying a Jerusalem home at a substantial discount from a developer in exchange for arranging construction permits for the builder. Olmert is a former mayor of Jerusalem.
Olmert has dismissed the various investigations as a political witch hunt. But the continuing investigations, along with a series of scandals involving some of his closest associates, have weakened him politically ahead of a U.S.-sponsored Mideast conference.
Israeli and Palestinian negotiators have been trying to work out the outlines of a future peace agreement ahead of the summit. But an indictment against Olmert would weaken his ability to maneuver and could possibly lead to the disintegration of the government.