[2] Afterwards, Nilsson moved to New York to become the Design Director for the Polo Ralph Lauren women’s wear collection.

[2][7] Anna Wintour wore one of his dresses to the Vogue Fashion Awards in October 2001,[8] and he was named Designer of the Year 2001 by New York magazine as well as being elected to the International Best-Dressed List by Eleanor Lambert and Vanity Fair.

[2] In 2003 Nilsson returned to Paris, joining Nina Ricci as their Creative Director of fashion, and perfume and cosmetics.

[2] He revitalized Nina Ricci to tap into a clientele of "uptown girls" and "the new generation of socialites“ who included Anne Hathaway, Renée Zellweger, Reese Witherspoon, Kate Beckinsale and Dita Von Teese[9][10][11][12] In 2004 he designed the brand's first ever resort collection and was able to raise attention for the brand through several international runway shows, trunkshows and soirées.

[23] In 2018 it was announced that Lars Nilsson would be collaborating with the iconic Swedish store, Svenskt Tenn, producing a range of luxury interior fabrics and home accessories.

[28] The Iris Collection got its name from the flower and was inspired by Nilsson's travels in England, notably the gardens of Sissinghurst and Great Dixter in Kent and East Sussex respectively, but also the Jardin des plantes in Paris.