Plyhm, previously known as Gustavsson, was a founder and the creative director of the now-defunct Stockholm digital shop Farfar. At SapientNitro, he will lead the creative work on the agency's Unilever account.
He will report to Malcolm Poynton, the chief creative officer, Europe.
At Farfar, Plyhm worked on the Milko Music Machine, which won awards including the Grand Prix at Cannes.
Plyhm has recently worked at Wieden & Kennedy as a freelance creative on the Nike business. He also worked at Agency Republic as a creative director on its O2 and Sony PlayStation accounts.
Poynton said: "Anders combines a level of digital, marketing and brand experience that's a rare find in today's line-up of creative leaders. He is not afraid of working ahead of the pack when it comes to conceiving and delivering new ways for brands to connect with consumers."