Picasso's "Women of Algiers (Version O)" and Giacometti's life-size "Pointing Man" were among dozens of masterpieces from the 20th century Christie's offered in a curated sale titled "Looking Forward to the Past."
Christie's global president, Jussi Pylkkanen, who was the auctioneer, said the two pieces are outstanding works of art.
"I've never worked with two such beautiful objects," he said.
The Picasso price, USD 179,365,000, and the Giacometti price, USD 141,285,000, included the auction house's premium. The buyers elected to remain anonymous.
More From This Section
Experts say the prices were driven by artworks' investment value and by wealthy collectors seeking out the very best works.
"I don't really see an end to it, unless interest rates drop sharply, which I don't see happening in the near future," Manhattan dealer Richard Feigen said.
Impressionist and modern artworks continue to corner the market because "they are beautiful, accessible and a proven value," added Sarah Lichtman, professor of design history and curatorial studies at The New School.
"I think we will continue to see the financiers seeking these works out as they would a blue chip company that pays reliable dividends for years to come," she said.
The most expensive artwork sold at auction had been Francis Bacon's "Three Studies of Lucian Freud," which Christie's sold for USD 142.4 million in 2013.
"Pointing Man," depicting a skinny 5-foot (1.5-metre)-high bronze figure with extended arms, has been in the same private collection for 45 years. Giacometti, who died in 1966, made six casts of the work; four are in museums, and the others are in private hands and a foundation collection. His "Walking Man I" had held the auction record for a sculpture. It sold for USD 104.3 million in 2010.