The pair will be joining Fallon from the Minneapolis agency Carmichael Lynch, where they recently won a Cannes Lion for their Harley-Davidson "faces" campaign.
Sorensen previously worked at Fallon, while Hansen worked at Hunt Murray and Kaufman Stewart in Minneapolis.
Kerry Feuerman, the executive creative director at Fallon, said: "It would be hard to find a better team of craftsmen than Hans and Eric. These guys get brands."