Christie's said the photos from a 1962 shoot were the last professional images taken of Monroe before she died that year of a drug overdose. They ran in Vogue instead as a memorial.
They're among more than 100 Monroe images being offered for sale at Christie's. The sale continues Wednesday.
Also at Christie's Tuesday, four Helmut Newton photographs, titled "They're Coming, Paris (Naked and Dressed)," sold for $662,500.
The buyers were anonymous.