The 'National Anthem' singer will front press advertisements and a commercial for the retailer's autumn campaign, which launches in September.
She is also set to record a cover of '50s classic 'Blue Velvet' that will be made available to fans on H&M's website.
The first images released show Del Rey posing in a pale pink sweater in a shoot described by H&M's creative director Donald Schneider as "very LA noir".
Explaining its decision to recruit her, H&M dubbed the 'Video Games' star as a "modern feminine woman with a soft attitude" who has quickly become "a style icon".
Del Rey's role with H&M was first reported last month when she was spotted shooting the campaign in New York.
Watch Lana Del Rey in the video for 'National Anthem' below: